Retrospective estimation of exposure to benzene in a leukaemia case-control study of petroleum marketing and distribution workers in the United Kingdom

FK506 (tacrolimus), a potent immunosuppressant, is used for inhibiting allograft rejection in the organ transplantation field. In a preclinical toxicity study in rats, FK506 induced various toxicities, including renal and pancreatic injuries. One of these toxic findings was cataract, and we have found that cataract appeared in rats dosed orally with FK506 for 13 weeks and more. Therefore, to better elucidate the onset mechanism of FK506-induced cataract, we measured biochemical parameters, such as sorbitol, Na,K-ATPase and glutathione in the lens of rats. Rats were dosed with FK506 in oral daily doses of 0.2, 1 or 5 mg/kg for 13 weeks, the lowest dose of which approximated the expected clinical dosage. Cataract developed in the 5-mg/kg/day group, with an incidence of 25%, whereas no cataract formation was observed in the 0.2- or 1-mg/kg/day groups. Five mg/kg/day led an increase of sorbitol and a decrease of reduced type glutathione, but did not affect Na,K-ATPase activity of the lens. FK506 is known to have diabetogenicity mediated through pancreatic injury, which appears as vacuolation of islet cell in rats. Five mg/kg/day of FK506 induced an elevation of blood glucose associated with glucose intolerance, and decrease of both basal insulin level and insulin content in the pancreas, and the changes were in parallel with the cataract development in the present study. On the other hand, diabetic parameters did not change in the 0.2- or 1-mg/kg/day groups. These observation suggest that diabetes developed in the rats dosed with 5 mg/kg/day of FK506. Coadministration of a novel aldose reductase inhibitor, Zenarestat, at an oral dose of 50 mg/kg/day resulted in a reduction of incidence of the FK506-induced cataract and a decrease of sorbitol levels in the lens when compared to that in the lens of rats dosed with 5 mg/kg/day of FK506. These results suggest that FK506-induced cataract in rats is due to an accumulation of sorbitol in the lens, secondary to the diabetogenic effect of FK506. FK506 treatment at the doses of 0.2 and 1 mg/kg/day neither affected parameters indicative of diabetes nor induced cataract in rats, suggesting that the cataract would not develop with FK506 if diabetic parameters were kept under control.     

The enhanced immunosuppressive efficacy of newly developed liposomal FK506 in canine liver transplantation

Local delivery of immunosuppressants to the graft and lymphatic tissue is a potential appraoch to enhance the immunosuppressive efficacy and to alleviate systemic adverse effects simultaneously. By taking advantage of this method, we developed liposomal FK506. Previous pharmacokinetic study of liposomal FK506 indicated increased FK506 levels in the liver and spleen. Because the liver is the site of the allograft in liver transplantation and the spleen is a major lymphoid tissue, we hypothesized that liposomal FK506 would increase immunosuppressive efficacy in liver transplantation. We evaluated this hypothesis in a canine model. Orthotopic liver transplantation was performed using beagle dogs, and the recipients were divided into the following groups: group I, no immunosuppression (n = 5); group II, 0.05 mg/kg/day of FK506 i.v. in a commercially available i.v. formulation for 14 days (n = 5); and group III, 0.05 mg/kg/day of FK506 i.v. in a liposomal formulation for 14 days (n = 5). All recipients in group I died within 2 weeks. Recipients in group II died within 33 days. In contrast, three recipients in group III survived for more than 200 days (P < 0.05 versus group I or group II). In DNA analysis, splenocyte proliferation activity in group III was significantly suppressed in comparison with group II. These results suggest that liposomal FK506 markedly increase the immunosuppressive efficacy of FK506 in liver transplantation. A local immunosuppressive effect in the grafted liver and significant suppression of splenocyte proliferation might contribute to enhancement of the immunosuppressive efficacy of liposomal FK506.     

FK 506 'rescue' immunosuppression for obliterative bronchiolitis after lung transplantation

PRELIMINARY EXPERIENCE: In a consecutive case series (level V evidence) involving 10 recipients of unilateral lung transplantation (LT) with bronchiolitis obliterans, in conjunction with Fujisawa protocol 93-0-003, the physiologic responses to FK 506 (tacrolimus) "rescue" immunosuppression were assessed. Recipients were 22+/-18 months post-LT and demonstrated progressive allograft dysfunction that was refractory to pulsed-dose methylprednisolone therapy. All recipients received induction immunosuppression with Minnesota antilymphocyte globulin (10 to 15 mg/kg/d) for 5 to 10 days, cyclosporine (CsA) (whole-blood Abbott TDX fluorescence polarization immunoassay (Abbott Inc, Abbott Park, IL)=600 to 800 ng/mL), azathioprine (2 mg/kg/d), and prednisone (tapered to 0.2 mg/kg/d). The "rescue" regimen consisted of oral FK 506 adjusted to maintain a whole-blood Abbott IMX microparticle enzyme immunoassay (Abbott Inc, Abbott Park, IL) of 10 to 15 ng/mL with an initial increase in prednisone (1.0 mg/kg/d) during conversion that was subsequently tapered to 0.2 mg/kg/d. Spirometry was performed monthly in accordance with accepted American Thoracic Society criteria. Recipients were classified in accordance with the International Society for Heart and Lung Transplantation (ISHLT) "Working Formulation for Standardization of Nomenclature and for Clinical Staging of Chronic Dysfunction in Lung Allografts" as stages Ib (n=2), IIb (n=4), and IIIb (n=4) upon entry to the protocol. The deltaFEV1/month relationships during CsA- and FK 506-based regimens were analyzed by linear regression and compared by signed rank test (p<0.05). RESULTS: The deltaFEV1/month slopes were -0.0687+/-0.0221 and +0.0300+/-0.033 L/mo (mean+/-SEM) for CsA and FK 506, respectively (p=0.037). Although no significant spirometric improvement was noted in most recipients, no further decline in FEV1 occurred after conversion to FK 506. Recipients with less severe chronic dysfunction (ie, obliterative bronchiolitis [OB] stages Ib and IIb) stabilized their spirometric indexes at higher levels. Two recipients with OB stage IIIb died of hypercapnic respiratory failure at 6 and 8 months after conversion. CONCLUSIONS: The deltaFEV1/mo slopes stabilized after FK 506 conversion. Earlier conversion may be beneficial in stabilizing FEV1 at a higher plateau. Significant economic impact may be anticipated with FK 506 compared to alternative cytolytic strategies for OB. However, multicenter prospective controlled investigations are necessary to further address the potential role of FK 506 after LT (level I evidence). Furthermore, the ISHLT "Staging of OB Syndrome" may have significant clinical implications vis-à-vis prognosis and potential therapies.     

Comparative dose-dependence study of FK506 and cyclosporin A on the rate of axonal regeneration in the rat sciatic nerve

The new immunosuppressant drug FK506 (Tacrolimus) increases the rate of nerve regeneration in vivo (Gold et al., 1994; Gold et al., 1995). In the present study, we have examined the dose-dependence of FK506's ability to enhance nerve regeneration. In the first set of experiments, rats received daily s.c. injections of FK506 (2 mg/kg, 5 mg/kg or 10 mg/kg) for 18 days after a sciatic nerve crush injury. Signs of functional recovery in the hind feet appeared earlier than in saline-treated control rats at all three FK506 dosage; recovery was maximally accelerated in the 5-mg/kg group. Light microscopy at 18 days after nerve crush revealed more regenerating myelinated fibers in FK506-treated rats than in controls; this was most apparent in the 5-mg/kg group. Morphometric analysis of axonal areas in the soleus nerve confirmed that axonal calibers were maximally increased in the 5-mg/kg group. In the second set of experiments, the rate of axonal regeneration was determined by radiolabeling the L5 dorsal root ganglion. Regeneration rate for sensory axons was maximally increased (by 34%) in the 5-mg/kg group. In contrast, cyclosporin A (10 or 50 mg/kg; dosages were selected on the basis of the 1/10 lower potency of cyclosporin A) did not significantly alter the rate of axonal regeneration. Cyclosporin A (50 mg/kg) also failed to increase functional recovery or axonal calibers in the soleus nerve. Because the two drugs share a common mechanism for producing immunosuppression (i.e., calcineurin inhibition), these results indicate that FK506's nerve regenerative property involves a distinct, calcineurin-independent mechanism.     

An experimental study of coronary arteriosclerosis after heart transplantation

The purpose of this study is to evaluate the effects of Cyclosporine (CsA), FK-506 (FK) and 15-Deoxyspergualin (DOS) on coronary arteriosclerosis after rat heart transplantation. Three groups of Lewis rats (n = 7, each) received heterotopic heart transplants from F-344 donors and were treated with CsA (Group Cs), FK (Group FK) and DOS (Group DOS) intraperitoneally. All rats were sacrificed 60 days later and assessed microscopic grading score (GS) of rejection and arteriosclerosis, and measured serum lipid. There was no significant difference in the GS of rejection but the GS of arteriosclerosis in the groups Cs was significantly higher than the group DOS (1.71 +/- 0.24 versus 1.11 +/- 0.34, p < 0.01). Triglyceride in the groups Cs was significantly higher than the group FK and group DOS (99 +/- 23 versus 66 +/- 21, 56 +/- 30 mg/dl, p < 0.02), and LDL in the group Cs and group FK was significantly higher than group DOS (104 +/- 17, 81 +/- 23 versus 31 +/- 17 mg/dl, p < 0.01). We concluded that DOS had a superior protective effect against coronary arteriosclerosis after heart transplantation and it may depend on the different mechanism of immunosuppression and lipid metabolism abnormality causing by immunosuppressants.     

Effect of immunosuppressant FK506 on ischemia-induced degeneration of hippocampal neurons in gerbils

To evaluate the effect of FK506 on delayed neuronal death in gerbils after forebrain ischemia, 84 adult Mongolian gerbils were used in this study. Transient forebrain ischemia was induced by clipping common carotid arteries bilaterally for 5 minutes. One hour after reperfusion we intraperitoneally injected FK506 (1.0 mg/kg), cyclosporin A (CsA) (10.0 mg/kg) or the vehicle solution into each gerbil. In one group, each agent was additionally administered daily 3 more times at 24, 48 and 72 hours after ischemia. The gerbils were killed 4 days or 10 days after transient ischemia, and damage to their hippocampal pyramidal cells was histologically assessed. Additionally, the body temperature was measured following administration of each drug to investigate drug-induced hypothermia. Post-ischemic repeated treatment with FK506 significantly (p < 0.01) reduced degeneration of hippocampal neurons. However, partial treatment did not modify neuronal degeneration. CsA did not show a neuroprotective effect in this study. Drug-induced mild hypothermia (35-37 C) was observed following administration of FK506 or CsA. There was no significant difference in the time course of the body temperature between the FK506 and CsA group. We demonstrated that the repeated FK506 treatment, but not the CsA treatment, reduced ischemia-induced degeneration of hippocampal neurons in gerbils. Although FK506-induced hypothermia might have modified neuronal degeneration, a comparison with CsA indicated that the neuroprotective effect of FK506 was not solely due to hypothermia per se.     

Effect of a novel immunosuppressant, FK 506, on autoimmune glomerulonephritis in Brown Norway rats

Mercuric-chloride (HgCl2) induces a lymphoproliferative disorder and autoimmune glomerulonephritis in Brown Norway rats. The effects of a new immunosuppressant FK 506 on this model of glomerulonephritis were studied. Brown Norway rats were treated with HgCl2 according to a standard protocol (HgCl2 1 mg/kg s.c. 3 times/ week). Rats developed proteinuria at day 7, which reached a plateau level at day 14. On day 14, renal histology showed prominent mesangial cellular proliferation and the expansion of mesangial matrix. Electron microscopic study showed the effacement of visceral epithelial foot processes and the microvillous transformation of the visceral epithelium. Immunofluorescence study showed a strong linear staining for IgG and the adhesion molecule ICAM-1 in all glomeruli. Coadministration of FK 506 (1 mg/kg s.c. daily) prevented the appearance of proteinuria at day 14 (621.4 +/- 30.5 vs. 2.2 +/- 2.7 mg/day) and the morphological lesions. These findings suggest that FK 506 could be useful for the therapy of certain types of human glomerulonephritis.     

Limb allograft in rats: studies on optimal maintenance dose of FK506 and development of graft-versus-host-disease (GVHD)

The optimal dose of FK506 on rat limb allograft was investigated across the BN-to-F344 histocompatibility barrier. BN limb allografts were rejected in untreated F344 hosts within 11 +/- 1 days (mean +/- SD) after operation. A single injection of 0.5 mg/kg, 1.0 mg/kg, or 2.0 mg/kg of FK506 on the day of transplantation significantly prolonged graft survival, mean survival times (MST) based on gross sign of skin rejection were 16 +/- 1 days, 19 +/- 1 days, 21 +/- 1 days, respectively. Maintenance doses of 0, 0.25, 0.5, 1.0, or 2.0 mg/kg/week of FK506 after a single administration of 10 mg/kg of FK506 on the day of limb allograft prolonged the graft survival, 63 +/- 10, 68 +/- 20, 87 +/- 23, 98 +/- 30, 136 +/- 20 days, respectively, and showed no evidence of infection or toxic side effects. The regimen of lower maintenance dose of FK506, however, developed chronic GVHD. In the second set of experiments, development of peripheral blood chimeras was studied in PVG-to-ACl limb allograft model. A single injection of 50 mg/kg of the day of transplantation prolonged graft survival and MST was 154 days. The average rates of peripheral blood chimeras were 2 to 6% and there was no relationship between graft survival and peripheral blood chimeras. However, GVHD developed in one of the six recipients at 201 days after operation. In the similar experiments, grafts were irradiated before operation. Peripheral blood chimeras was not observed in there experiments and GVHD was not developed in 300 days after operation. These data suggest that FK506 is quite effective for rat limb allograft survival in dose-dependent manner and GVHD could be prevented by graft irradiation before operation.     

Myocardial viability. Concept, physiopathology. Methods and diagnostic value]

This study was designed to investigate the effect of tacrolimus (FK506) and of cyclosporine (CsA) on tubular function in renal graft recipients. Patients were randomised after renal transplantation to immunosuppressive treatment with FK506 (n = 8) or CsA (n = 8). Patients had a mean age of 45.7 +/- 3.4 yr; there was no difference in age, sex, HLA status or CMV mismatches. Neither was there any difference in the frequency of episodes of acute kidney failure between the groups, nor was there a significant difference in the frequency of episodes of kidney rejection within the first year. The mean FK506 level at the time lay at 14.7 +/- 14.4 ng/mL whole blood, and the mean CsA level at the time of study was 162 +/- 25 ng/mL whole blood. We performed renal function studies 6 months after transplantation: CIn, CPAH, NaHCO3 loading, and Na2SO4 loading. There was no significant impairment of GFR in patients treated with FK506 with 53.6 +/- 2.5 mL/min as compared to 58 +/- 6 mL in group 2. Plasma renin activity (0.6 +/- 0.4 ng/mL vs 2.3 +/- 3; p < 0.01) and aldosterone (69 +/- 17 vs 157 +/- 28.2 pg/mL; p < 0.05) were significantly decreased during treatment with FK506. Fractional HCO3 excretion was low in both groups, indicating that bicarbonate reabsorption in the proximal nephron was unimpaired. Distal renal tubular acidosis was demonstrated in 4 patients of group 1 but in only 1 of group 2. Potassium levels were slightly increased in patients treated with FK506 (5.4 +/- 0.2 mmoL/L) as compared to cyclosporine (4.9 +/- 0.3 mmoL/L; p < 0.05). Distal hydrogen ion secretion, evaluated by the ability to increase urinary pCO2 in a highly alkaline urine, was impaired in patients treated with FK506 (U-B pCO2: 16.1 +/- 4 vs 36 +/- 5.8; p < 0.05) as compared to patients treated with CsA. The maximum acidification capability (NAE) was slightly lowered during therapy with FK506 (67.5 +/- 11.8 versus 86.6 +/- 16.5 mumoL/min, ns). We conclude that FK506 administration results in a decrease in the rate of hydrogen ion secretion by the collecting tubules. This defect was disclosed by the finding of a subnormal pCO2 in a highly alkaline urine. These results show that FK506 is able to induce distal tubular acidosis. Distal tubular acidosis is part of FK506 induced nephrotoxicity, the pathogenesis of this type of hyperkalemic metabolic acidosis found in patients treated with FK506 after renal transplantation has to be further elucidated.     

The significance of eating patterns: an elderly Greek case study

BACKGROUND: Endothelin-1 (ET-1), a novel vasoconstrictor, possibly plays a role in the mediation of ischemia/reperfusion (I/R) injury. Tacrolimus (FK506) and cyclosporin A (CsA) were reported to maintain tissue microcirculation of the liver subjected to I/R. This study investigated the effects of these immunosuppressants on intestinal I/R in terms of intestinal tissue microcirculation associated with ET-1. METHODS AND RESULTS: Male S-D rats were pretreated twice with FK506 (0.2 mg/kg), CsA (10 mg/kg) or only saline solution (0.5 mL). The tissue microcirculation in the control was reduced after I/R (29% +/- 10%) accompanied by hypotension, increased tissue ET-1 expression (25.0% +/- 6.4% to 67.9% +/- 5.0% 60 minutes after reperfusion), and increased ET-1 level in the portal blood (3.4 +/- 0.9 to 23.6 +/- 6.1 pg/mL). FK506 suppressed ET-1 expression (27.3% +/- 5.2%, 4.1 +/- 2.2 pg/mL), maintained microcirculation (96% +/- 16%), and blood pressure, reduced histologic damage, and improved survival. CsA had a similar but weaker effect compared with FK506. An additional experiment was performed with BQ485Na (BQ), an ETA receptor antagonist, to evaluate the genuine role of ET-1. BQ showed almost the same effects as FK506. CONCLUSIONS: FK506 and CsA, particularly the former, maintain microcirculation and protect the tissue from I/R injury by suppressing the production and release of ET-1.     

Two-day quadruple therapy for cure of Helicobacter pylori infection: a comparative, randomized trial

PURPOSE: Small intestinal transplantation remains a significant clinical problem. Allogeneic fetal intestinal (AFI) transplantation shows promise, particularly regarding procurement; however, no studiesto date have evaluated the potential success of true allogeneic loci implantation. The authors hypothesized that isolated segments of AFI could be heterotopically transplanted but would require immunosuppression to survive. METHODS: Donor tissue was obtained from late-gestation Brown Norway rat fetuses with a histo-locus RTN and Fischer fetuses with a histo-locus RT1L. The recipients were adolescent male Fischer rats with a histo-locus RT1L. A 1.2-cm segment of fetal small bowel was implanted in the omentum of the recipient rat and allowed to mature for 5 weeks. Animals were then separated into five groups. Group A served as controls with syngeneic fetal intestinal (SFI) transplant. Group B received AFI with no immunosuppression; group C, AFI transplant with five days of FK506; group D, AFI with 10 days of FK506; and Group E, AFI with daily FK506 for the entire 5-week maturation period. Animals were killed on day 35. RESULTS: All animals gained weight over the maturation period. Groups B, C, and D had no viable transplant segments at day 35. Groups A and E both had well-developed viable segments confirmed by gross and histological evaluation. CONCLUSIONS: FK506 allows for normal intestinal development for use in allogeneic fetal bowel transplantation. With this observation, the use of fetal intestine transplanted into the portal circulation emerges as a potentially viable alternative to present intestinal transplant models.     

Immunosuppressants decrease neutrophil chemoattractant and attenuate ischemia/reperfusion injury of the liver in rats

BACKGROUND: Neutrophils may play an important role in the development of liver ischemia/reperfusion injury. We investigated the effects of the immunosuppressants azathioprine (AZA), cyclosporine A (CsA), tacrolimus (FK506), and rapamycin (RPM) on the expression of cytokine-induced neutrophil chemoattractant (CINC) after ischemia/reperfusion of the liver. METHODS: Liver ischemia was induced in male Wistar rats by occluding the portal vein with a microvascular clip for 30 minutes. Rats received two intramuscular injections of AZA (4 mg/kg), CsA (5 mg/kg), FK506 (0.5 mg/kg), or RPM (0.5 mg/kg) 3 and 24 hours before ischemia/reperfusion of the liver. RESULTS: Serum CINC concentrations in untreated animals increased, peaked 6 hours after reperfusion, and thereafter decreased gradually. Pretreatment with AZA, CsA, FK506, and RPM, however, inhibited the increase in serum CINC concentrations after reperfusion. CINC mRNA in liver tissue increased and peaked 3 hours after reperfusion, but was significantly lower in animals treated with AZA, CsA, FK506, and RPM. In vitro CINC production by Kupffer cells harvested from animals treated with AZA, CsA, FK506, or RPM 3 hours after reperfusion was also significantly lower than that observed in untreated animals. Both myeloperoxidase activity and the number of neutrophils accumulating in the liver 24 hours after reperfusion in animals treated with AZA, CsA, FK506, and RPM were significantly lower than in untreated animals. This correlated with lower serum aspartate transaminase, alanine transaminase, and lactate dehydrogenase levels in animals treated with AZA, CsA, FK506, and RPM 24 hours after reperfusion. CONCLUSION: The immunosuppressants AZA, CsA, FK506, and RPM reduce neutrophil accumulation and attenuate ischemia/reperfusion injury of the liver.     

Protective effect of FK506 on ischemia/reperfusion-induced myocardial damage in canine heart

We investigated the cardioprotective effect of FK506, a newly developed immunosuppressive agent, on ischemia-reperfusion-induced myocardial damage and the inhibitory effect of FK506 on superoxide radical formation by neutrophils. Open-chest anesthetized dogs were divided into two groups: group 1, 2-h occlusion of the coronary artery followed by 1-h reperfusion; and group 2, 2-h occlusion followed by 1-h reperfusion with preadministration of FK506 (0.5 mg/kg). After reperfusion, heart mitochondria were prepared from the normal and reperfused areas and mitochondrial function and mitochondrial GSH (the reduced form of glutathione) and GSSG (the oxidized form of glutathione) concentrations were measured. In addition, neutrophils were collected from normal healthy dogs, and the inhibitory effect of FK506 on superoxide radical formation by neutrophils was also investigated. One-hour reperfusion after 2-h coronary occlusion induced significant mitochondrial dysfunction associated with a marked depletion of mitochondrial GSH concentration. FK506 reduced mitochondrial dysfunction, depletion of mitochondrial GSH concentration, and development of reperfusion arrhythmias. FK506 also reduced stimulant-induced superoxide radical formation by normal neutrophils dose dependently. Radical scavenging activity decreased in association with reperfusion, and FK506 reduced superoxide radical formation by neutrophils, which might contribute to lessening ischemia-reperfusion damage.     

Nephrotoxicity studies of the immunosuppressants tacrolimus (FK506) and ascomycin in rat models

The nephrotoxic potential of ascomycin, the C21-ethyl analogue of FK506, was defined and ways explored to enhance its detection. After 14-day dosing in the Fischer-344 rat, FK506 and ascomycin reduced creatinine clearance by >50% at doses of 1 and 3 mg/kg, i.p., respectively. Ascomycin also had a 3-fold lower immunosuppressive potency in a popliteal lymph node hyperplasia assay, resulting in an equivalent therapeutic index consistent with a common mechanistic dependence on calcineurin inhibition. Renal impairment with different routes of administration was correlated with pharmacokinetics. Sensitivity of detection was not adequate with shorter dosing durations in rats with unilateral nephrectomy or in mice using a cytochrome P-450 inhibitor, SKF-525A. In 14-day studies, nephrotoxicity was not induced by continuous i.p. infusion of ascomycin at 10 mg/kg/day or daily oral administration (up to 50 mg/kg/day) in rats on a normal diet, nor by continuous i.v. infusion (up to 6 mg/kg/day) in rats on a low salt diet to enhance susceptibility. The lack of toxicity at high oral doses of FK506 or ascomycin, and the finding of non-linear oral pharmacokinetics of ascomycin show that this drug class has an oral absorption ceiling. The negative results with continuous infusion suggest that ascomycin nephrotoxicity is governed by peak drug levels. In addition to defining ways to meaningfully compare the nephrotoxic potential of FK506 derivatives, these results have implications for overall safety assessment and improved clinical use.     

Induction of hepatic poly(ADP-ribose) polymerase by peroxisome proliferators, non-genotoxic hepatocarcinogens

The binding capacity of FK506 binding protein (FKBP) was examined after 2-h hemispheric ischemia in the gerbil brain in order to clarify the precise mechanism of the neuroprotective effects of FK506. Firstly, the FK506 binding was evaluated in vitro in the normal gerbil brain using 1 nM [3H]dihydro-FK506 as a specific ligand. FK506 binding sites were distributed in a rather homogeneous manner, although the greatest binding was noted in the hippocampus CA1. Secondly, Scatchard analysis demonstrated that the binding sites of FK506 could be composed of two components in each brain region. Thirdly, 18 Mongolian gerbils were divided into two groups: an ischemia group (n = 12) and a sham group (n = 6). The right common carotid artery was ligated to induce hemispheric ischemia for 2 h in the ischemia group. The local cerebral blood flow was measured at the end of the experiment by the [14C]iodoantipyrine method. The ligated animals with levels of local cerebral blood flow in the lateral nuclei of the thalamus of less than 50 ml/100 g/min were utilized as the ischemia group (n=6) for further data analysis. No significant differences in FK506 binding between the ischemia and sham groups were observed in any regions. The above data indicate that the binding capacity of FKBP tends to remain normal during 2-h ischemia, suggesting that FK506 may exert its neuroprotective effects through its binding to FKBP in the brain during the early phase of cerebral ischemia.     

Comparison of the stability of technetium-labeled peptides to challenge with cysteine

-Tacrolimus (FK 506) is a powerful, widely used immunosuppressant. The clinical utility of FK 506 is complicated by substantial hypertension and nephrotoxicity. To clarify the mechanisms of FK 506-induced hypertension, we studied the chronic effects of FK 506 on the synthesis of endothelin-1 (ET-1), the expression of mRNA of ET-1 and endothelin-converting enzyme-1 (ECE-1), the endothelial nitric oxide synthase (eNOS) activity, and the expression of mRNA of eNOS and C-type natriuretic peptide (CNP) in rat blood vessels. In addition, the effect of the specific endothelin type A receptor antagonist FR 139317 on FK 506-induced hypertension in rats was studied. FK 506, 5 mg. kg-1. d-1 given for 4 weeks, elevated blood pressure from 102+/-13 to 152+/-15 mm Hg and increased the synthesis of ET-1 and the levels of ET-1 mRNA in the mesenteric artery (240% and 230%, respectively). Little change was observed in the expression of ECE-1 mRNA and CNP mRNA. FK 506 decreased eNOS activity and the levels of eNOS mRNA in the aorta (48% and 55%, respectively). The administration of FR 139317 (10 mg. kg-1. d-1) prevented FK 506-induced hypertension in rats. These results indicate that FK 506 may increase blood pressure not only by increasing ET-1 production but also by decreasing NO synthesis in the vasculature.     

Toxicities of tacrolimus and cyclosporin A after allogeneic blood stem cell transplantation

To determine how well tacrolimus (FK506) and cyclosporin A (CsA) are tolerated after HLA-identical blood stem cell transplantation, we performed a retrospective review of 87 adults transplanted consecutively who received FK506 (n = 40) or CsA (n = 47) in a nonrandomized fashion in combination with methylprednisolone for graft-versus-host disease (GVHD) prophylaxis and compared the incidences of complications potentially related to the immunosuppressive agents. Pre-transplant demographic characteristics, drug compliance and rates of acute GVHD were comparable for the two groups. Following first discharge, fewer patients in the FK506 group required antihypertensive therapy (32 vs 59%, P = 0.022), but more required insulin (34 vs 10%, P = 0.014). There was also a trend for more hyperkalemia and less moderate-to-severe venoocclusive disease in the FK506 group. However, nephrotoxicity, neurotoxicity, hemolytic-uremic syndrome, and cytomegaloviral or fungal infections through the first 100 days post-transplant did not differ significantly between the two groups. We conclude that for allogeneic blood stem cell transplant recipients, the incidence of complications related to FK506 and CsA in equally effective dose schedules in combination with methylprednisolone are similar with the exception of the risks of hypertension and hyperglycemia.     

Functional and structural characteristics of experimental FK 506 nephrotoxicity

1. FK 506 (Tacrolimus, Prograf) is a novel immunosuppressant which is effective in solid organ transplantation and autoimmune diseases. The lack of a suitable animal model has hindered the study of the nephrotoxicity of the drug which has emerged as a common adverse effect in clinical trials. We report both acute and chronic nephrotoxicity with tacrolimus (FK) in which renal structure and function are worsened by sodium depletion. 2. Pair fed male Sprague-Dawley rats were given FK (3 or 6 mg/kg, p.o.) or vehicle for 7, 21 and 42 days on low salt or normal diet. The FK whole blood trough levels achieved (3-10 ng/mL) were similar to those observed in FK treated transplant patients. 3. In salt depleted animals treated for 7 days, FK (6 mg/kg) decreased renal blood flow and glomerular filtration rate (1.8 +/- 0.1 and 0.2 +/- 0.1 mL/min per 100 g vs 2.9 +/- 0.2 and 1.1 +/- 0.1 mL/min per 100 g in the vehicle group, P < 0.01). 4. After 21 days of treatment of FK on low salt diet but not normal salt, FK induced focal collapse and vacuolization in proximal tubules and discrete or confluent zones of tubulointerstitial oedema and mononuclear cell infiltration. 5. After 42 days in salt depleted rats, there was significant tubulointerstitial scarring that was associated with an increased plasma renin activity (PRA) (64 +/- 10 vs 30 +/- 4 ng AI/mL per h in the vehicle group, P < 0.05). Animals given normal salt diets did not develop significant histological lesions even up to 42 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improving results of pediatric renal transplantation

BACKGROUND: Outcome after renal transplantation in children has been variable. We undertook a retrospective study of our experience over the past five years. STUDY DESIGN: From January 1, 1988, to October 15, 1992, 60 renal transplantations were performed upon 59 children at the Children's Hospital of Pittsburgh. Twenty-eight (47 percent) of the kidneys were from cadaveric donors, and 32 (53 percent) were from living donors. The recipients ranged in age from 0.8 to 17.4 years, with a mean of 9.8 +/- 4.8 years. Forty-six (77 percent) recipients were undergoing a first transplant, while 14 (23 percent) received a second or third transplant. Eight (13 percent) of the patients were sensitized, with a panel reactive antibody of more than 40 percent. Eleven of the 14 patients undergoing retransplantation and seven of the eight patients who were sensitized received kidneys from cadaveric donors. Thirty-three (55 percent) patients received cyclosporine-based immunosuppression, and 27 (45 percent) received FK506 as the primary immunosuppressive agent. RESULTS: The median follow-up period was 36 months, with a range of six to 63 months. The one- and four-year actuarial patient survival rate was 100 and 98 percent. The one- and four-year actuarial graft survival rate was 98 and 83 percent. For living donor recipients, the one- and four-year actuarial patient survival rate was 100 and 100 percent; for cadaveric recipients, it was 100 and 96 percent. Corresponding one- and four-year actuarial graft survival rates were 100 and 95 percent for the living donor recipients and 96 and 69 percent for the cadaveric recipients. Patients on cyclosporine had a one- and four-year patient survival rate of 100 and 97 percent, and patients on FK506 had a one- and three-year patient survival rate of 100 and 100 percent. Corresponding one- and four-year actuarial graft survival rates were 100 and 85 percent in the cyclosporine group, while one- and three-year actuarial graft survival rates were 96 and 84 percent in the FK506 group. The mean serum creatinine level was 1.24 +/- 0.64 mg per dL; the blood urea nitrogen level was 26 +/- 13 mg per dL. The incidence of rejection was 47 percent; 75 percent of the rejections were steroid-responsive. The incidence of cytomegalovirus was 10 percent. The incidence of post-transplant lymphoproliferative disorder was 8 percent. None of the patients on cyclosporine were able to be taken off prednisone; 56 percent of the patients receiving FK506 were taken off prednisone successfully. Early growth and development data suggest that the patients receiving FK506 off prednisone had significant gains in growth. CONCLUSIONS: These results support the idea that renal transplantation is a successful therapy for end-stage renal disease in children. They also illustrate the potential benefits of a new immunosuppressive agent, FK506.     

Vancomycin pharmacokinetics in neonates and infants: a retrospective evaluation

OBJECTIVE: To evaluate the frequency with which current loading and maintenance vancomycin dosages achieve target serum concentrations based on pharmacokinetic parameters obtained after the initial dose. Also, to identify the daily vancomycin dosage necessary to achieve target serum concentrations at steady-state and to determine if any relationships exist between vancomycin pharmacokinetic parameters and various patient characteristics. SETTING: Neonatal intensive care unit (NICU) at Georgia Baptist Medical Center. PATIENTS/METHODS: Twenty-three infants with suspected or documented gram-positive infection who received intravenous vancomycin between July 1990 and November 1991 were included in this retrospective analysis. Gestational age range from 23 to 41 weeks and postconceptional age (PCA) at the time of the study ranged from 26 to 46 weeks. Vancomycin therapy was initiated with a loading dose of 15 mg/kg, followed by a maintenance dosage of 20-30 mg/kg/d, which was usually given as 10 mg/kg q8-12h. All vancomycin doses were administered using a syringe pump. Peak and trough serum concentrations were obtained following the first dose. Vancomycin pharmacokinetic parameters were determined using a one-compartment model. Infants receiving indomethacin within two weeks prior to study were analyzed separately (group 2, n = 4). All other infants were included in group 1 (n = 19). RESULTS: For group 1, vancomycin clearance (Cl), volume of distribution (Vd), and half-life were (mean +/- 1 SD) 0.072 +/- 0.032 L/kg/h, 0.52 +/- 0.08 L/kg, and 5.6 +/- 1.6 hours, respectively. For both groups, loading doses provided 1-hour postinfusion peak concentrations of 25-35 mg/L in one of every two infants studied, whereas only three percent of initial maintenance doses were projected to provide desired peak and trough concentrations at steady-state. For group 1, the mean daily dosage necessary to provide target peak (25-35 mg/L) and trough (5-10 mg/L) concentrations at steady-state was larger than that initially prescribed (29.6 +/- 13.1 vs. 22.2 +/- 4.7 mg/kg/d). For group 2, the mean daily dosage required to achieve target peak and trough concentrations at steady-state was smaller than that initially prescribed (14.8 +/- 4.3 vs. 20.0 +/- 0.1 mg/kg/d) and was exactly half of that required for group 1. Excellent correlations were observed between PCA and vancomycin Cl (L/h) (r = 0.92; p < 0.0001), body weight and Vd(L) (r = 0.94; p < 0.0001), body weight and vancomycin Cl (L/h) (r = 0.85; p < 0.0001), PCA and Vd (L) (r = 0.89; p < 0.0001), and body surface area and Vd (L) (r = 0.93; p < 0.0001) for group 1. Moderate correlations were also noted between PCA and Cl relative to body weight (L/kg/h), postnatal age and Cl (L/kg/h), and PCA and vancomycin dosage requirements (mg/kg/d). No linear correlation was observed between any patient characteristic and Vd standardized for body weight. CONCLUSIONS: Our data demonstrate the need for a more accurate method of estimating initial vancomycin dosage requirements in this NICU population. Although some of the relationships revealed in this study could be used to determine vancomycin dosage for infants in the range of approximately 30-36 weeks PCA, we hesitate to suggest this approach presently because of the potential limitations of our study design. Further prospective study is needed to confirm these observations. In addition, further study is necessary to describe the time course of the interaction between vancomycin and indomethacin in infants with successful and unsuccessful closure of their patent ductus arteriosus.