Cytotoxicity and cell-proliferation induced by the nephrocarcinogen hydroquinone and its nephrotoxic metabolite 2,3,5-(tris-glutathion-S-yl)hydroquinone

Hydroquinone, an intermediate used in the chemical industry and a metabolite of benzene, is a nephrocarcinogen in the 2-year National Toxicology Program bioassay in male Fischer 344 rats. Current evidence suggests that certain chemicals may induce carcinogenesis by a mechanism involving cytotoxicity, followed by sustained regenerative hyperplasia and ultimately tumor formation. Glutathione (GSH) conjugates of a variety of hydroquinones are potent nephrotoxicants, and we now report on the effect of hydroquinone and 2,3,5-(tris-glutathion-S-yl)hydroquinone, on site-selective cytotoxicity and cell proliferation in rat kidney. Male Fischer 344 rats (160-200 g) were treated with hydroquinone (1.8 mmol/kg or 4.5 mmol/kg, p.o.) or 2,3,5-(tris-glutathion-S-yl)hydroquinone (7.5 micromol/kg; 1.2-1.5 micromol/rat, i.v.), and blood urea nitrogen (BUN), urinary gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase (ALP), glutathione-S-transferase (GST) and glucose were measured as indices of nephrotoxicity. Hydroquinone (1.8 mmol/kg, p.o.) is nephrotoxic in some rats, but not others, but cell proliferation (BrDU incorporation) in proximal tubular cells of the S3M region correlates with the degree of toxicity in individual rats. At 4.5 mmol/kg, hydroquinone causes significant increases in the urinary excretion of gamma-GT, ALP and GST. Pretreatment of rats with acivicin prevents hydroquinone-mediated nephrotoxicity, indicating that toxicity is dependent on the formation of metabolites that require processing by gamma-GT. Consistent with this view, 2,3,5-(tris-glutathion-S-yl)hydroquinone, a metabolite of hydroquinone, causes increases in BUN, urinary gamma-GT and ALP, all of which are maximal 12 h after administration of 2,3,5-(tris-glutathion-S-yl)hydroquinone. In contrast, the maximal excretion of GST and glucose occurs after 24 h. By 72 h, BUN and glucose concentrations return to control levels, while gamma-GT, ALP and GST remain slightly elevated. Examination of kidney slices by light microscopy revealed the presence of tubular necrosis in the S3M segment of the proximal tubule, extending into the medullary rays. Cell proliferation rates in this region were 2.4, 6.9, 15.3 and 14.3% after 12, 24, 48 and 72 h, respectively, compared to 0.8-2.4% in vehicle controls. Together with the metabolic data, the results indicate a role for hydroquinone-thioether metabolites in hydroquinone toxicity and carcinogenicity.     

Effect of a protective-ventilation strategy on mortality in the acute respiratory distress syndrome

Recent studies have shown that tetrafluoroethylene is a renal and hepatic carcinogen in the rat. In this study, we have examined the ability of a single i.p. dose of 1,1,2,2-tetrafluoroethyl-L-cysteine (TFEC), a major metabolite of tetrafluoroethylene, to produce hepatic and renal injury in male and female rats. We have also examined the effect of blocking the renal organic anion transport system with probenecid and of inhibiting the activity of cysteine conjugate beta-lyase with aminooxyacetic acid on the extent of renal injury produced by TFEC. Doses of > or = 12.5 mg/kg TFEC produced renal tubular necrosis to the pars recta of the proximal tubules within 24 h in both male and female rats. This was associated with an increased kidney to body weight ratio and plasma urea at doses of > or = 25 mg/kg. No consistent evidence of liver injury was seen at doses up to 50 mg/kg TFEC in rats of either sex, although occasional vacuolation of hepatocytes and a small dose-related increase in liver to body weight ratio was observed. Prior treatment of female rats with probenecid completely prevented the renal injury produced by either 25 or 50 mg/kg TFEC as judged by plasma urea and histopathology. However, prior treatment of female rats with aminooxyacetic acid afforded no protection against the nephrotoxicity produced by either TFEC or the cysteine conjugate of hexachloro-1,3-butadiene. Thus no major sex difference in nephrotoxicity in the rat was seen with TFEC, while accumulation of TFEC, or its N-acetyl derived metabolite, into renal proximal tubular cells via a probenecid sensitive transport system appears to be a key event in the mechanism of nephrotoxicity. The lack of protection observed with the cysteine conjugate beta-lyase inhibitor, aminooxyacetic acid, may reflect the inability to completely inhibit the mitochondrial form of this enzyme and thereby prevent the formation of the reactive metabolite. Our acute studies provide no insight concerning the liver carcinogenicity of tetrafluoroethylene.     

An increase in renal dopamine production after the administration of radiographic contrast agents

Renal vasoconstriction and anti-natriuresis conditioned by radiographic contrast agents (CA) may be antagonised by the administration of exogenous dopamine. However, the influence of CA on the activity of renal synthesis of dopamine has not been studied. This study assessed the daily urinary excretion of dopamine, its precursor. L-3, 4-dihydroxyphenylaline (L-DOPA), and its metabolites (acid 3, 4-dihydroxyphenylacetic, DOPAC; homovanillic acid, HVA) 24 hours before and 48 hours following administration of a non ionic and hyposmolar (lopromide) CA in patients (n = 10; average age 61.3 +/- 4.3 years) submitted to coronary angiography. Urinary excretion of noradrenalin, a marker of sympathetic activity, was also assessed during the same period. The deputation of creatinine (Ccr) and the urinary excretion of sodium (UNa+) lowered after the administration of the CA (Ccr, 79.2 +/- 10.2 vs 72.2 +/- 9.6 ml/min/1.73 m2, p < 0.05; UNa+, 112.8 +/- 9.6 vs 61.7 +/- 25.1 mmol/24 h, p < 0.05). On the contrary, the urinary excretion of potassium increased in the period of 24 h following the administration of the AC (31.7 +/- 5.2 vs 103.8 +/- 10.8 mmol/24 h, p < 0.05). There was an increase in the urinary excretion of dopamine as well as noradrelalin during the 24 hour period following the administration of the CA (dopamine, 1260.2 +/- 196.8 vs 1571.5 +/- 170.2 mmol/24 h p < 0.5; noradrenalin, 186 +/- 36.6 mmol/24 h, p < 0.05). On the contrary, the urinary excretion of L-DOPA lowered after the administration of the CA (115.4 +/- 25.5 vs 80.5 +/- 13.2 mmol/24 h, p < 0.05). These results conditioned an increase in the dopamine/L-DOPA ratio in the urine, after the administration of the CA (12.2 +/- 1.5 vs 22.2 +/- 4.5 mmol/24 h, p < 0.05). In conclusion, the administration of CA is accompanied by an increase in the renal production of dopamine which, in these conditions, may act as a compensatory natriuretic hormone.     

Formation of catechol estrogen glutathione conjugates and gamma-glutamyl transpeptidase-dependent nephrotoxicity of 17beta-estradiol in the golden Syrian hamster

In an animal model of hormone-mediated carcinogenesis, male golden Syrian hamsters develop renal carcinoma following prolonged exposure to 17beta-estradiol. The basis for the species and tissue specificity is unclear. Detailed information on the disposition of 17beta-estradiol in this model is lacking. Because catechol estrogens have been implicated in this model of carcinogenesis, we investigated the metabolism and nephrotoxicity of 17beta-estradiol in golden Syrian hamsters, with emphasis on the formation of catechol estrogen thioethers. 17beta-Estradiol (50 micromol/kg, i.p.) is a mild nephrotoxicant, causing significant elevations in the urinary excretion of gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase, glutathione S-transferase (GST) and glucose. Increases in renal protein carbonyls and lipid hydroperoxides, which are markers of oxidative damage, also occur after administration of 17beta-estradiol (50 micromol/kg, i.p.). 17beta-Estradiol-mediated nephrotoxicity is reduced by treating animals with acivicin, an inhibitor of gamma-GT, implying that toxicity is mediated by metabolites requiring metabolism by this enzyme. Following administration of 17beta-[14C]estradiol (100 micromol/kg) to hamsters, 9.7% of the dose is recovered in bile after 5 h, the majority (7.9%) representing aqueous metabolites. Seven catechol estrogen GSH conjugates were identified, 2-hydroxy-1,4-bis-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-estrone, 2-hydroxy-1-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-17beta-estradiol, and 2-hydroxy-1-(glutathion-S-yl)-17beta-estradiol. At 5.4 micromol/kg of 17beta-estradiol, a dose-reflective of daily exposure levels in the hamster model of nephrocarcinogenicity, 12% of the dose is recovered within 5 h as a combination of GSH conjugates of 2- and 4-hydroxy-17beta-estradiol and 2- and 4-hydroxyestrone. In summary, oxidation of catechol estrogens, followed by GSH conjugation, occurs in vivo and 17beta-estradiol is a mild nephrotoxicant in a manner dependent on the activity of gamma-GT.     

Bone marrow and renal injury associated with haloalkene cysteine conjugates in calves

Almost 40 years ago, it was reported that cattle-feed which had been extracted with hot trichloroethylene and then fed to calves produced renal injury and a fatal aplastic anaemia. The toxic factor was subsequently identified as S-(1,2-dichlorovinyl)-L-cysteine (DCVC). These original findings have been confirmed, a single intravenous dose of DCVC at 4 mg/kg, or 0.4 mg/kg intravenously per day administered for 10 days to calves produced aplastic anaemia, and renal injury after a single dose of 4 mg/kg. The toxicity to calves of a number of other haloalkene cysteine conjugates has been examined to ascertain whether, like DCVC, they produce bone marrow and renal injury. Intravenous administration of the N-acetyl cysteine conjugate of DCVC produced renal but not bone marrow injury at a molar equivalent dose to DCVC, indicating that the calf can deacetylate the mercapturic acid and further that sufficient chemical had reached the kidney to be a substrate for the enzyme cysteine conjugate beta-lyase. However, intravenous administration of the alpha-methyl analogue of DCVC, which cannot undergo metabolism via the enzyme cysteine conjugate beta-lyase, was without toxicity at doses about five-fold higher than DCVC. These latter findings provide strong evidence that metabolism of DCVC via the enzyme beta-lyase is necessary for bone marrow and renal injury to occur. The cysteine conjugates of perchloroethylene and hexachloro-1,3-butadiene(HCBD) when given intravenously to calves at molar equivalent doses to DCVC, or above, did not produce either bone marrow or renal injury. In contrast, intravenous administration of the cysteine conjugate of tetrafluoroethylene (TFEC) produced severe renal tubular injury in calves without affecting the bone marrow. In vitro studies with these haloalkene cysteine conjugates showed, like DCVC, that they were good substrates for calf renal cysteine conjugate beta-lyase and toxic to renal cells as judged by their ability to reduce organic anion and cation transport by slices of calf renal cortex and inhibit the renal enzyme glutathione reductase. Calves were also dosed either orally or intravenously with HCBD to assess its toxicity. HCBD at higher molar equivalent doses than DCVC produced mid-zonal necrosis in the liver, renal tubular necrosis but no bone marrow injury in calves. The key findings emerging from these studies are (1) that none of the other cysteine conjugates, at molar equivalent doses to DCVC and above, produce bone marrow injury in calves, (2) TFEC produced only renal injury, suggesting that sufficient of the other conjugates had not reached the kidney for metabolism by beta-lyase to produce cytotoxicity and (3) that HCBD itself is more toxic than its cysteine or mercapturic acid conjugate, suggesting that pharmaco-kinetics and disposition are important factors in determining the toxicity of these conjugates to calves. Further studies are needed to understand the basis for the selective toxicity of DCVC to the bone marrow of calves.     

Oxygen free radicals are not the main factor in experimental gentamicin nephrotoxicity

As a role for oxygen free radicals has been suggested in gentamicin (G) nephrotoxicity, we tested the hypothesis that exogenously administered glutathione (GSH), able to restore intracellular antioxidant potential, could be useful in reducing damage. Adult Sprague-Dawley rats were injected with saline (n = 30), subcutaneous (s.c.) G 100 (n = 23) and 150 mg/kg/day (n = 14), or s.c. G at the same dosages plus intraperitoneal (i.p.) GSH 1200 mg/kg/day (n = 24 and 14, respectively) for 7 days. In the G-100-day protocol, GSH-treated rats showed significantly lower renal G content (2.79 +/- 0.8 vs. 3.61 +/- 1.4 micrograms/mg prot) coupled with lower plasma urea (153 +/- 79 vs. 188 +/- 61 mg/dL) and creatinine levels (1.63 +/- 1 vs. 2.45 +/- 1 mg/dL). As to renal oxidant/antioxidant balance, local GSH was increased (0.32 +/- 0.01 vs. 0.19 +/- 0.01 microgram/mg prot) while lipid peroxidation, determined by production of thiobarbituric acid reactive substances (TBARS), was decreased (0.35 +/- 0.02 vs. 0.52 +/- 0.02 nmol/mg prot). In the G-150-mg protocol, GSH-treated rats showed no differences in renal gentamicin content or in blood urea and creatinine levels, in spite of a significantly lower renal TBARS production and a significantly higher GSH content. Urine enzyme excretion did not significantly change in GSH-treated vs. not-GSH-treated rats in both protocols. We conclude that: (a) GSH interferes with G nephrotoxicity mainly via a reduction in G uptake; (b) the oxidative renal stress is not crucial in inducing renal damage. In fact, when increased G dosages blunt the ability of GSH in reducing G uptake, no substantial protection is demonstrated.     

Right colonic diverticulitis: US and CT findings--new insights about frequency and natural history

BACKGROUND: Sevoflurane undergoes Baralyme- or soda lime-catalyzed degradation in the anesthesia circuit to yield compound A (2-[fluoromethoxy]-1,1,3,3,3-pentafluroro-1-propene), which is nephrotoxic in rats and undergoes metabolism via the cysteine conjugate beta-lyase pathway in those animals. The objective of these experiments was to test the hypothesis that compound A undergoes beta-lyase-dependent metabolism in humans. METHODS: Human volunteers were anesthetized with sevoflurane (1.25 minimum alveolar concentration, 3%, 2 l/min, 8 h) and thereby exposed to compound A. Urine was collected at 24-h intervals for 72 h after anesthesia. Rats, which served as a positive control, were given compound A intraperitoneally, and urine was collected for 24 h afterward. Human and rat urine samples were analyzed by 19F nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry for the presence of compound A metabolites. RESULTS: Analysis of human and rat urine showed the presence of the compound A metabolites S-[2(fluoromethoxy)-1,1,3,3,3-pentafluoropropyl]-N-acetyl-L- cysteine, (E)- and (Z)-S-[2-(fluoromethoxy)-1,3,3,3-tetrafluoro-1-propenyl]-N-acetyl- L-cysteine, 2-(fluoromethoxy)-3,3,3-trifluoropropanoic acid, 3,3,3-trifluorolactic acid, and inorganic fluoride. The presence of 2-(fluoromethoxy)3,3,3-trifluoropropanoic acid and 3,3,3-trifluorolactic acid in human urine was confirmed by gas chromatography-mass spectrometry. CONCLUSIONS: The formation of compound A-derived mercapturates shows that compound A undergoes glutathione S-conjugate formation. The identification of 2-(fluoromethoxy)-3,3,3-trifluoropropanoic acid and 3,3,3-trifluorolactic acid in the urine of humans anesthetized with sevoflurane shows that compound A undergoes beta-lyase-dependent metabolism. Metabolite formation was qualitatively similar in both human volunteers anesthetized with sevoflurane, and thereby exposed to compound A, and in rats given compound A, indicating that compound A is metabolized by the beta-lyase pathway in both species.     

Effect of experimental diabetes mellitus on gentamicin-induced acute renal functional changes in the anaesthetized rat

1. Rats with streptozotocin (STZ) diabetes are protected from gentamicin (GEN) nephrotoxicity. Because the chronic renal damage from GEN is preceded by acute renal functional changes (notably hypercalciuria), the present study aims to determine whether diabetes may also protect against the acute effects of the drug. If there is a link between the rapid physiological actions of GEN and its subsequent nephrotoxicity, the former may also be affected by the diabetic condition. 2. Standard renal clearance techniques were performed on anaesthetized rats that had been injected with STZ or vehicle 2 weeks previously. All animals were infused with 0.9% NaCl for 5 h and then either GEN (0.28 mg/kg per min) or 0.9% NaCl alone for 2 h. 3. Baseline fractional calcium excretion (FE(Ca)) of diabetic rats was three-fold that of control animals (6.6+/-0.2 vs 2.2+/-0.2%, respectively; P<0.01, MANOVA). Following GEN infusion, a comparable increase in FE(Ca) occurred in control and diabetic rats (5.3+/-0.6 vs 5.3+/-0.8%, respectively; NS). 4. Streptozotocin diabetes, therefore, does not alter the acute hypercalciuric response to GEN. This may suggest that the acute effects of GEN on renal calcium handling do not contribute to the subsequent nephrotoxicity. However, the higher baseline FE(Ca) seen in diabetic rats may afford protection against the renal injury caused by gentamicin.     

Effect of oral calcium loading on intact PTH and calcitriol in idiopathic renal calcium stone formers and healthy controls

The calciuric response after an oral calcium load (1000 mg elemental calcium together with a standard breakfast) was studied in 13 healthy male controls and 21 recurrent idiopathic renal calcium stone formers, 12 with hypercalciuria (UCa x V > 7.50 mmol/24 h) and nine with normocalciuria. In controls, serum 1,25(OH)2 vitamin D3 (calcitriol) remained unchanged 6 h after oral calcium load (50.6 +/- 5.1 versus 50.9 +/- 5.0 pg/ml), whereas it tended to increase in hypercalciuric (from 53.6 +/- 3.2 to 60.6 +/- 5.4 pg/ml, P = 0.182) and fell in normocalciuric stone formers (from 45.9 +/- 2.6 to 38.1 +/- 3.3 pg/ml, P = 0.011). The total amount of urinary calcium excreted after OCL was 2.50 +/- 0.20 mmol in controls, 2.27 +/- 0.27 mmol in normocalciuric and 3.62 +/- 0.32 mmol in hypercalciuric stone formers (P = 0.005 versus controls and normocalciuric stone formers respectively); it positively correlated with serum calcitriol 6 h after calcium load (r = 0.392, P = 0.024). Maximum increase in urinary calcium excretion rate, delta Ca-Emax, was inversely related to intact PTH levels in the first 4 h after calcium load, i.e. more pronounced PTH suppression predicted a steeper increase in urinary calcium excretion rate. Twenty-four-hour urine calcium excretion rate was inversely related to the ratio of delta calcitriol/deltaPTHmax after calcium load (r = -0.653, P = 0.0001), indicating that an abnormally up-regulated synthesis of calcitriol and consecutive relative PTH suppression induce hypercalciuria.(ABSTRACT TRUNCATED AT 250 WORDS)     

Activity of cathepsin B and collagenase in urine and excretion of fibronectin and TGF-beta 1 in urine of patients with membranous glomerulonephritis

In 30% cases nephrotic syndrome is due to membranous glomerulonephritis (MG). Fifty percent of patients reveal end stage renal disease in 15 years follow-up. The another 50% gain persistent remission. The pathogenesis of disease is not known. Protein accumulation in glomeruli leads to progressive loss of kidney structure and function in MG. Also the role of tissue proteolytic systems and growth factors in this process is not known. We aimed to estimate urine cathepsin B, collagenase activity and urine excretion of TGF-beta 1 and fibronectin in MG. MG patients revealed increased urine cathepsin B activity (10.58 +/- 8.73 pmol AMC/mg creatinine/min. vs. control 7.11 +/- 2.05 pmol AMC/mg creatinine/min. [p < 0.05]), urine collagenase activity (8.59 +/- 4.26 pmol AMC/mg creatinine/min. vs. control 3.84 +/- 2.09 pmol AMC/mg creatinine/min. [p > 0.02]) and increased urine excretion of fibronectin (214 +/- 335 ng/mg creatinine vs. control 12.7 +/- 6.7 ng/mg creatinine [p < 0.05]) and increased urine excretion of TGF-beta 1 (283.55 +/- 248.13 pg/ml vs. control 36.11 +/- 48.01 pg/ml [p < 0.05]). The results indicates on glomerular overproduction of TGF-beta 1 and urinary leak of proteolytic enzymes which may exacerbate glomerular proteolytic activity in MG. This may lead to glomerular protein accumulation and progressive loss of kidney function and structure in MG. Increased urine fibronectin excretion in MG patients seems to confirm the hypothesis.     

Factors relating to urinary protein excretion in children with autosomal dominant polycystic kidney disease

Adults with autosomal dominant polycystic kidney disease (ADPKD) who have overt proteinuria (>300 mg/d) have higher mean arterial pressures, lower creatinine clearances, larger renal volumes, and a more aggressive course of renal disease than ADPKD patients without proteinuria. This study examines the relationship between proteinuria and microalbuminuria and similar factors in ADPKD children. A total of 189 children from 81 ADPKD families was included in the analysis. The ADPKD children (n = 103) had significantly greater urine protein excretion rates than the non-ADPKD children (n = 86) (3.9+/-0.3 versus 2.8+/-0.2 mg/m2 per h, P < 0.001). Children with severe renal cystic disease (> 10 cysts; n = 54) had greater protein excretion than those with moderate disease (< or = 10 cysts; n = 49) (4.4+/-0.5 versus 3.3+/-0.2 mg/m2 per h, P < 0.05). The ADPKD children had significantly greater albumin excretion rates than the non-ADPKD children (32+/-6 versus 10+/-2 mg/m2 per 24 h, P < 0.001), and a higher percentage of ADPKD children had significant microalbuminuria (>15 mg/m2 per 24 h in boys and >23 mg/m2 per 24 h in girls) than their unaffected siblings (30% versus 10%, P < 0.05). Thirty percent of ADPKD children had albuminuria and 23% had overt proteinuria. For all ADPKD children, there was no correlation between proteinuria and hypertension. However, there was a significant correlation between urinary protein excretion and diastolic BP among children diagnosed after the first year of life (r = 0.23, P < 0.05). Therefore, proteinuria and albuminuria occur early in the course of ADPKD and may be markers of more severe renal disease.     

Renal proximal disfunction based on activity of n-acetyl-beta-d-glucosaminidase in urine of patients with kidney failure

N-acetyl-beta-D-glucosaminidase (NAG) urine activities of 63 patients with stable and unstable chronic renal failure have been investigated. The values of NAG activity obtained from these patients were compared with NAG activity of 33 normal controls. Abnormal NAG values (> 70 nmol/mg of creatinine) were found in 60 (95.2%) patients with chronic renal failure and the median of all values was 327.8 nmol/mg of creatinine. It was 14-fold greater than the median of values for normal controls. There were any significant differences of NAG values between the patients with massive proteinuria (> 1.5 g/24 h), moderate proteinuria and those without 24 hour proteinuria or non-significant proteinuria (respectively 423.5 +/- 286.3 vs 414.4 +/- 334.8 vs 453.0 +/- 451.3 nmol/mg of creatinine). There was no significant difference between the two subgroups of patients with NAG values above and below 280 nmol/mg of creatinine in age, gender, serum urea and uric acid levels. However, the incidence of patients with NAG values higher than 280 nmol/mg of creatinine was statistically significant in unstable course of renal insufficiency and raised serum creatinine levels. It is suggested that the measurement of NAG excretion may be helpful to monitor unstable process in renal failure.     

Excretion of neuraminic acid-containing trisaccharides in the urine during pregnancy

The excretion of neuraminic acid-containing trisaccharides in the urine during the course of normal pregnancy was studied. Neuraminyl-lactose and neuraminyl-galactosyl-(l led to 4)-N-acetylglucosamine were identified, and their excretion patterns were analyzed by thin-layer and gas chromatography. A progressive increase in the outputs of these acidic oligosaccharides was observed during the course of pregnancy in all cases studied. Neuraminyl-lactose excretion increased threefold, from 13.7 +/- 1.75 to 37.1 +/- 2.56 mg/24 h, and neuraminyl-galactosyl-N-acetylglucosamine twofold, from 8.4 +/- 1.27 to 15.3 +/- 2.21 mg/24 h (Mean +/- S.E.).     

Effects of a nitric oxide synthesis inhibitor on renal sodium handling and diluting capacity in humans

BACKGROUND: Inhibition of nitric oxide (NO) synthesis has antinatriuretic and antidiuretic effects. Limited information is available on the role of NO in tubular sodium transport in the human kidney. METHODS: We studied nine healthy, sodium-replete males with clearance techniques during maximal diuresis. NG-monomethyl-L-arginine (L-NMMA, 3 mg/kg priming dose plus 3 mg/kg/h) was infused for 3 h, to achieve steady-state inhibition of NO synthesis. Data were compared with a time control study. RESULTS: The effects of L-NMMA were quickly established and persisted through the entire infusion period. Mean arterial pressure increased slightly from 85+/-3 to 91+/-3 mmHg (P<0.05). Renal plasma flow decreased substantially, and glomerular filtration rate slightly. Large decreases in absolute sodium excretion, from 79+/-10 to 34+/-5 micromol/min (P<0.01), and fractional sodium excretion, from 0.5+/-0.0 to 0.3+/-0.0% (P<0.01), were associated with significant reductions in fractional lithium excretion (P<0.05) and maximum urine flow (P<0.01). Minimal urine sodium concentration decreased from 5.8+/-0.04 to 3.9+/-0.4 mmol/l (P<0.01) whereas minimal urine osmolality increased (P<0.05). Plasma renin activity, aldosterone and atrial natriuretic peptide levels did not change, whereas urinary excretions of guanosine 3'5'-cyclic monophosphate and of nitrite plus nitrate decreased slightly. CONCLUSIONS: Inhibition of endogenous NO synthesis in humans to an extent that raises blood pressure only mildly causes antinatriuresis, that can be attributed to increases in sodium reabsorption both at proximal and distal nephron sites. In addition, renal diluting capacity decreases. The effects in the diluting segment have not been reported before, and may be due to medullary vasoconstriction, similar to that described for angiotensin II.     

Diagnosis of thoracic outlet syndrome in the emergency department

Gadodiamide at a dose of 0.1 mmol/kg was administered intravenously to 10 renal transplanted patients with stable, impaired, or slowly deteriorating renal function (serum creatinine 194-362 mumol/l). The patients were referred for contrast medium enhanced magnetic resonance imaging to rule out possible graft circulation abnormalities. The excretion of gadodiamide in urine was prolonged as compared with healthy controls. After 120 h 92% of the injected dose was excreted in urine and only 0.4% in faeces. The plasma clearance of gadodiamide was 28.6 +/- (SD) 5.5 ml/min (n = 10), and the renal clearance (0-72 h) was 26.3 ml/min. The renal clearance of 125I-iothalamate for the same time period was 27.9 +/- 5.3 ml/min. Thus, gadodiamide is eliminated by glomerular filtration also in renal transplant patients with moderately to severe impaired renal function, and gadodiamide clearance may serve as an alternative marker for the determination of the glomerular filtration rate. Serum values of creatinine and beta(2)-microglobulin and creatinine clearance were unchanged by gadodiamide and neither was the urinary enzyme excretion significantly changed. These results suggest that the renal tolerance to gadodiamide is good also in renal transplant patients with impaired renal function.     

Isolation and identification of mercapturic acids of cinnamic aldehyde and cinnamyl alcohol from urine of female rats

Rats dosed with cinnamic aldehyde (I) excreted two mercapturic acids in the urine. The major one was identified as N-acetyl-S-(1-phenyl-3-hydroxypropyl)cysteine (V). The minor one was identified as N-acetyl-S-(1-phenyl-2-carboxy ethyl)cysteine (VI). The ratio appeared to be V : VI = 4 : 1. The hydroxy mercapturic acid (V) was also isolated from urine of rats dosed with cinnamyl alcohol (II). The total mercapturic acid excretion as percentage of the dose was 14.8 +/- 1.9% for cinnamic aldehyde (250 mg/kg) (n = 4) and 8.8 +/- 1.7% for cinnamyl alcohol (n = 4) (125 mg/kg). Inhibition of the alcohol dehydrogenase by pyrazole (206 mg/kg) diminished the thioether excretion of cinnamyl alcohol to 3.3 +/- 1.4% of the dose (n = 8). Cinnamic aldehyde has been proposed to be an intermediate in the mercapturic acid formation of cinnamyl alcohol.     

Dose-dependent induction or depression of cysteine conjugate beta-lyase in rat kidney by N-acetyl-S-(1,2,3,4,4-pentachloro-1,3-butadienyl)-L-cysteine

The influence of N-acetyl-S-(1,2,3,4,4-pentachloro-1,3-butadienyl)-L-cysteine (NAc-PCBD) on cysteine conjugate beta-lyase in female rat kidney has been examined. After a single, non-nephrotoxic dose of NAc-PCBD (3 mg/kg), cytosolic beta-lyase enzyme activity was increased 1.5 to 3-fold commensurate with a corresponding increase in enzyme protein levels as assessed by both Western blot and ELISA analyses. Using a cDNA probe for beta-lyase, this induction was found to be accompanied by an increase in the cognate mRNA. In contrast, a higher, nephrotoxic dose of NAc-PCBD (10 mg/kg) decreased all the above parameters. These effects appeared to be specific to the cytosolic form of the enzyme as no changes in kidney mitochondrial beta-lyase or enzyme protein levels were observed. Repeated dosing with the lower dose level (3 mg/kg) resulted in either no change, or in some instances, a reduction in the above parameters, suggesting an accumulation of the xenobiotic and a masking of the induction phenomenon. The molecular mechanisms underlying these observations are discussed in terms of the nephrotoxicity of halogenated xenobiotics.     

Insulin resistance precedes microalbuminuria in patients with insulin-dependent diabetes mellitus

BACKGROUND: Insulin resistance has been associated with hypertension and with renal complications in patients with type 1 diabetes mellitus. Causal relationships have not been fully explained. METHODS: We investigated whether insulin resistance precedes microalbuminuria by measuring insulin resistance with a euglycaemic clamp in combination with indirect calorimetry in 16 uncomplicated type 1 diabetic patients and in six healthy control subjects. The patients had over 10 year duration of diabetes, and were expected to experience either a complication-free or complicated disease course within the next few years. They have thereafter been followed for the development of microalbuminuria for 3 years. RESULTS: In a euglycaemic insulin clamp glucose disposal was lower in diabetic patients compared with control subjects (7.5 +/- 2.9 and 12.6 +/- 2.0 mg/kg LBM/min; P<0.002), mainly due to impaired glucose storage (4.3 +/- 2.3 vs 8.6 +/- 1.6 mg/kg LBM/min; P<0.001). Three years later seven IDDM patients had albumin excretion rate over 30 mg/24 h; glucose disposal (5.5 +/- 2.1 vs 9.0 +/- 2.2 mg/kg LBM/min; P<0.01) had been lower in patients who developed microalbuminuria compared with those who remained normoalbuminuric. CONCLUSIONS: Insulin resistance predicts the increment in urinary albumin excretion. Insulin resistance depends mainly on impaired glucose storage in uncomplicated IDDM.     

Probenecid protects against In vivo acetaminophen-induced nephrotoxicity in male Wistar rats

Renal effects of acetaminophen (APAP) were studied in rats pretreated with probenecid to analyze whether acute APAP-induced nephrotoxicity could be related to a probenecid-sensitive transport system for APAP or its S-derived conjugates. The administration of probenecid (200 mg/kg b.wt. i.p.) 30 min before APAP administration (1000 mg/kg b.wt. i.p.) improved urine flow rate and protected against the alterations on glomerular filtration rate and urea and creatinine plasma levels induced by APAP. Fewer epithelial cells and granular casts and a decrease in the urinary excretion of protein and glucose were observed in rats pretreated with probenecid. Probenecid pretreatment promoted an elevation in the urinary 16-hr excretion of APAP and a diminution in the plasma levels attained by APAP. These results suggest that protection afforded by probenecid in vivo could be a consequence of the inhibition of APAP S-conjugate renal uptake and/or an increase in APAP renal clearance. The effects of APAP in presence of probenecid were studied with the isolated perfused kidney model. Perfusion with probenecid (0.1 mM) before APAP (10 mM) did not change APAP direct renal effects, APAP urinary excretion, or APAP renal clearance relative to glomerular filtration rate. Our results suggest that protection afforded by probenecid in vivo could be the result of the inhibition of the uptake of nephrotoxic APAP metabolites and/or a diuresis-induced enhanced APAP renal excretion.     

Consequences of selective blockade of septal noradrenergic afferents on anxiety and spatial working memory performance in mice

We have previously reported a high prevalence of endemic renal tubular acidosis (EnRTA) in the northeast of Thailand, and our subsequent studies provided evidence that K deficiency exists in the same region. Since tubulointerstitial damage is associated with K deficiency, we postulate that this might be implicated in the pathogenesis of EnRTA and, if so, that a spectrum of tubulointerstitial abnormalities can be anticipated. In this study we evaluated renal acidification ability in 4 patients and in 11 of their relatives. We used a 3-day acid load (NH4Cl 0.1 g/kg/day) followed by 20 mg oral furosemide and monitored the maximal renal concentrating ability using water deprivation and intranasal 1-deamino-D-arginine vasopressin. The results showed that the subjects could be divided into three groups; normal relatives of the patients, those with suspected renal tubular acidosis, and patients with overt EnRTA who had chronic metabolic acidosis and a low rate of excretion of NH4+. The rate of excretion of K was very low (20 +/- 4 mmol/day) in patients with EnRTA and in their relatives with suspected EnRTA. The transtubular K concentration gradient was also very low in their relatives, especially in patients with suspected EnRTA (2.8 +/- 0.2). With a 3-day NH4Cl load, the rate of excretion of NH4+ was very low in patients with EnRTA (32 +/- 9 mmol/day), and the relatives with suspected EnRTA also had a decreased capacity to excrete NH+4 (50 +/- 14 mmol/day). In contrast, the normal relatives excreted 92 +/- 12 mmol of NH+4/day. The patients with EnRTA could lower their urine pH to less than 5.5 after the acid loading (6.2 +/- 0.3). After furosemide (20 mg), the NH4+ excretion in the patients with EnRTA was lower than in the normal relatives. Moreover, the minimum urine pH in patients with EnRTA did not fall (6.1 +/- 0.2), but there was a fall to 4.8 +/- 0.1 in the patients with suspected EnRTA after furosemide treatment. In conclusion, there was a spectrum of tubulointerstitial abnormalities ranging from suspected to overt distal RTA in a geographic area known to have a high prevalence of K deficiency. K deficiency might be the important pathogenetic factor of EnRTA in the northeast of Thailand.