The pulmonary uptake of intravenously administered liposomal alpha-tocopherol is augmented in acute lung injury

The present study was carried out to investigate whether the intravenous administration of liposomal alpha-tocopherol can result in a significant localization of the antioxidant in the injured lung. Male Sprague-Dawley rats were injected with paraquat dichloride (20 mg/kg, ip.) and 4, 24 or 48 h later, they were given an intravenous injection of a liposomal alpha-tocopherol preparation (20 mg alpha-tocopherol in 128 mumoles liposomal lipid/kg) labelled with [14C]dipalmitoylphosphatidylcholine (DPPC) and [3H]alpha-tocopherol. Animals were killed and their lungs removed for analysis 24 h after liposomal treatment. To demonstrate whether the extent of uptake of radioactive alpha-tocopherol liposomes was directly related to the extent of residual lung injury, additional groups of animals were also injected with higher doses (30 and 40 mg/kg body weight) of paraquat dichloride and 48 h later, were treated with liposomal alpha-tocopherol; animals were then killed 24 h after liposomal alpha-tocopherol treatment. The intraperitoneal injection of paraquat dichloride resulted in time- and dose-dependent decreases in angiotensin converting enzyme and alkaline phosphatase activities suggesting that the toxicant injures both the capillary endothelial cells and alveolar type II epithelial cells, respectively. The recovery of intravenously administered radioactive alpha-tocopherol in the lungs of saline-treated animals was found to be about 2% of the initial dose 24 h post-liposomal treatment. However, in paraquat-treated animals, there was an increased localization of the labelled alpha-tocopherol to the lung, resulting in a difference of pulmonary delivery by as much as 2-3 fold compared to that in a normal lung. The 3H/14C ratio, representing the recovery of [3H]alpha-tocopherol and [14C]liposomes, was practically constant and there was a linear relationship between the measurable lung injury index and the corresponding recovery of radiolabelled alpha-tocopherol in the lung. Our results appear to suggest that the residual pulmonary injury augments the delivery of liposomal alpha-tocopherol to the lung.     

Micropuncture studies of glucose transport in the dog: mechanism of renal glycosuria

Clearance and micropuncture studies were performed in 23 dogs without glucose loading to examine the tubule mechanism of renal glycosuria. Studies were carried out in three groups of animals before and after 10% extracellular volume expansion, and administration of maleic acid in low dose at 150 mumol/kg and in high dose at 300 mumol/kg. Specific hexokinase methods were used for the determination of glucose in tubule fluid and urine. Under control conditios, glucose reabsorption occurred predominantly in the proximal tubule. In all three groups, proximal tubule reabsorption of both sodium and glucose was inhibited in the second phase, showing a good correlation between the two. In contrast, fractional urinary glucose excretion remained unchanged after volume expansion and low-dose maleic acid, indicating reabsorption of virtually all the increased glucose load at a further "distal" site. On the other hand, significant glycosuria developed after high-dose maleic acid that was a result of reduced glucose reabsorption in the distal nephron, in addition to the proximal effect. It was concluded that distal glucose transport plays a significant role in regulating urinary glucose excretion and maintains renal thershold for glucose,     

Modification of vancomycin nephrotoxicity by other antibiotics in rats

Vancomycin (VCM) was intravenously administered to rats for 14 days at doses of 150 mg/kg/day and 250 mg/kg/day alone or in combination with 1,000 mg/kg/day of latamoxef (LMOX), flomoxef (FMOX) or cefpirome (CPR) or 250 mg/kg/day of fosfomycin (FOM), and the influences of combined antibiotics on the VCM-induced renal damage were studied. The renal impairment caused by VCM alone was, morphologically, demonstrated mainly as regeneration of tubular epithelium: slight regeneration was observed in a half of rats administered 150 mg/kg/day and slight to extensive regeneration in all the rats administered 250 mg/kg/day. Clinical examinations found apparent increases in urinary LDH and MDH activities in rats administered 250 mg/kg/day, thus showing a good correlation with renal pathological changes. In addition, increase in kidney weight and increase in urinary NAG activity were noted, while changes in plasma urea-N and creatinine were mild, and gamma-GTP activity and protein in urine could not be used as a parameter of the renal impairment. The slight renal impairment as noted in rats administered VCM 150 mg/kg/day alone was not observed at all when LMOX or FMOX was administered concomitantly, and less pronounced even when FOM was administered concomitantly. When CPR was administered concomitantly, the changes were the same as those observed with VCM alone. The renal impairment in rats administered VCM 250 mg/kg/day was apparently less severe when combined with LMOX, FMOX and FOM than that in rats administered VCM alone, and this was supported by apparent reduction of clinical examination values as the parameter of VCM-induced nephrotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum proinsulin in normal and gestational diabetic pregnancy

The tubular transport of urate and sodium was examined by clearance, free-flow micropuncture, intratubular microinjection and precession techniques in control rats and in rats receiving a new uricosuric diuretic, indanyloxyacetic acid (MK-196). The i.v. infusion of MK-196 (50 mg/kg of body wt/hr) resulted in significant increases in the fractional excretion of sodium (FENa) from 0.98 +/- 0.01 to 11.86 +/- 2.88% (P less than 0.001) and in FEurate from 14.1 +/- 1.03 to 56.0 +/- 2.86% (P less than 0.001). End-proximal tubular fluid to plasma inulin (TF/Pinulin) ratios were 2.43 +/- 0.15 and 2.51 +/- 0.10 in control and drug-treated animals, respectively (P = NS). Total urinary urate recovery after MK-196 administration was higher following microinjections of [2-14C] urate into early proximal tubule sites: 70.5 +/- 2.7% in controls vs. 84.9 +/- 0.9 (P less than 0.001), and after microinjections into late proximal tubule sites: 82.8 +/- 2.9% vs. 91.3 +/- 1.9 (P less than 0.05). Urinary precession of urate from inulin was demonstrable following placement of isotopes of these compounds on the surface of the kidney in controls, but was abolished by MK-196. This agent, therefore, inhibits the reabsorption and secretion of urate in the proximal convoluted tubule, the net effect being a marked increase in urinary urate excretion. By contrast, its inhibitory effect on sodium reabsorption is exerted at a site or sites distal to the accessible portion of the proximal tubule. The demonstration of reduced urate reabsorption and normal sodium reabsorption in the proximal tubule suggests that the reabsorption of these constituents of the glomerular filtrate is not intimately linked at this nephron site.     

Glutamine transaminase K intranephron localization in rats determined by urinary excretion after treatment with segment-specific nephrotoxicants

Glutamine transaminase K(GTK) excretion assessed in urine and by kidney histology was evaluated in rats after single treatment with 1.0 mg/kg i.p. of mercuric chloride, 100 mg/kg i.p. of hexachloro-1:3-butadiene (both S3, pars recta, segment-specific nephrotoxicants) and 25 mg/kg s.c. of potassium dichromate (S1-S2, pars convoluta, segment-specific nephrotoxicant). The aim was to correlate segment-specific injury and enzyme excretion in order to assess, using non-vasive methods, localization of GTK along the proximal tubule. Mercuric chloride and hexachloro-1:3-butadiene produced early focal damage in the pars recta (focal necrosis was shown 10 h after treatment, and diffuse necrosis appeared later at 34 and 24 h after treatment). Changes of the pars convoluta were occasional and delayed (72 h after treatment for both substances). On the contrary, potassium dichromate induced damage of the pars convoluta (vacuolar degeneration and focal necrosis were evident 24 h and 48 h after treatment, respectively), whereas the pars recta was affected later (focal vacuolar degeneration was observed 72 h after treatment). Increase urinary GTK excretion was early after treatment with mercuric chloride and hexachloro-1:3-butadiene (significant increase was observed within 10 h), with a peak for both substances 24 h after treatment, in agreement with the necrosis of the pars recta. Potassium dichromate induced a significant increase of enzyme excretion in urine also 24 h after injection, according to histological features showing vacuolar degeneration of the pars convoluta; the peak of excretion was reached 48 h after treatment (delay was due, probably, to s.c. administration). The results show that GTK increased in urine after treatment with S3 and S1-S2 specific nephrotoxicants; the combination of histological examination and urinary enzyme supports the evidence that the enzyme is distributed along the whole of the proximal tubule.     

Effect of Ambilhar (niridazole) on spermatogenesis in guinea-pigs

Niridazole (Ambilhar), a new antibilharzial drug was fed for 5 days to 20 male guinea pigs at 50 mg/kg while testicular and epididymal biopsies were examined histologically for 10 weeks. Only 10 animals survived the treatment. On the 5th day sperm numbers were reduced in testis tubules. On Day 8 variations in tubule size and in degrees of inhibition of spermatogenesis were at their maximum. Some tubules had recovered spermatogenesis at 15 days, and all had at 3 weeks. Guinea pigs are more sensitive to niridazole than are rats.     

Induction of rabbit renal mixed-function oxidases by phenobarbital: cell specific ultrastructural changes in the proximal tubule

Administration of phenobarbital (60 mg/kg) daily for 4 days to male rabbits resulted in induction of renal cytochrome P-450 (3.5-fold) and a corresponding increase in ethoxycoumarin-O-deethylase and benzphetamine-N-demethylase activity (17- and 4-fold, respectively). Kidney weight to body weight ratio and renal ethoxyresorufin-O-deethylase were not affected by phenobarbital pretreatment. Numerous focal areas of proliferation of smooth endoplasmic reticulum (SER) were evident in proximal tubule cells from phenobarbital treated rabbits while proximal tubular cells from control rabbits had only small and sparcely located aggregates of SER. Phenobarbital-induced SER proliferation was specifically localized to the S3 segment of the proximal tubule. Proliferation was not observed in S2 cells of the proximal tubule, cells of Henle's loop, distal tubules, or collecting tubules in rabbits pretreated with phenobarbital. These data demonstrate the biochemical heterogeneity of cell types within the proximal tubules of rabbits. Furthermore, induction of mixed-function oxidases specifically in S3 cells of the proximal tubule may be of toxicological significance in the metabolic activation of certain nephrotoxicants.     

Renal sodium reabsorption following induction of recovery from volume expansion

In the rat, infusion of a volume of isotonic saline equal to 2% of body weight resulted in an 82% increase in delivery of filtrate out of the proximal tubule but little or, in some animals, no change in the urinary excretion of sodium. By contrast, further degrees of volume expansion resulted in lesser increases in the distal delivery of filtrate, but were associated with a marked increase in the urinary excretion of sodium. Sixty minutes following completion of volume expansion, while the animals were still in positive sosium balance, the urinary excretion of sodium decreased 52% compared to a decrease of only 24% in the distal delivery of filtrate. During the course of progressive volume expansion and during the recovery phase, there was a dissociation between alterations in sodium reabosrption in the proximal convoluted tubule and in the whole kidney. These studies indicate that although the proximal tubule is more sensitive to changes in the extracellular fluid volume, distal nephron sites are ultimately responsible both for the natriuresis of volume expansion and the relative antinatriuresis of the recovery periods.     

Oncogenicity studies of piperonyl butoxide in rats and mice

1. The oncogenicity of Piperonyl butoxide (PBO) has been studied in the mouse and rat. CD-1 mice were administered PBO in the diet at target doses of 0, 30, 100 and 300 mg/kg/day for 79 weeks and Sprague-Dawley rats 0, 30, 100 and 500 mg/kg/day for 104/105 weeks. 2. At termination of the study in the mouse there was evidence of increased liver weights and an increased incidence of eosinophilic adenomas at 100 and 300 mg/kg/day in males and 300 mg/kg/day in females. 3. In rats there was increased liver weights at 100 and 500 mg/kg/day associated with hepatocyte hypertrophy in both male and female rats. There was no increased incidence of neoplasia at any site. Hypertrophy and hyperplasia of thyroid follicles was observed at 500 mg/kg/day in both sexes. 4. The observations reflect the expected changes related to the induction of the mixed function oxygenase group of enzymes. In the mouse the increased incidence of eosinophilic adenomas is not considered relevant for human risk evaluation.     

Chronic exposure to morphine does not alter the neural tissues subserving its acute rewarding properties: Apparent tolerance is overshadowing.

Drug-naive, but not morphine-dependent, rats preferred places paired with morphine (2 mg/kg) over unfamiliar neutral places. Both drug-naive and morphine-dependent rats preferred places paired with higher doses of morphine (20 mg/kg) over unfamiliar places. Lesions of the tegmental pedunculopontine nucleus (TPP) blocked the conditioned place preferences produced by both 2 and 20 mg/kg morphine in drug-naive rats but not the preferences produced by 20 mg/kg morphine in dependent rats. When morphine-dependent animals received withdrawal-alleviating doses of morphine (20 mg/kg) 3.5 hrs before pairing one environment with 2 mg/kg morphine, they showed morphine-conditioned place preferences that were abolished by TPP lesions. The apparent behavioral tolerance to the TPP-mediated rewarding effects may have resulted from overshadowing by separate withdrawal-related motivational mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ligation of the left renal vein in epm1-Wistar rats: functional and morphologic alterations in the kidneys, testes and suprarenal glands

OBJECTIVE: The ligation of the left renal vein (LLVR) in man is a controversial procedure in view of the risks of lesion to the renal parenchyma. With the objective of studying the morphologic and functional alterations caused by these lesions, we conducted experimental research with rats. MATERIAL AND METHODS: 64 male adult EPM1-WISTAR rats were used, divided into 8 groups-4 for LLRV and four for control. Each LLRV group and corresponding control group were sacrificed progressively on the 7th, 15th, 30th and 60th day after the initial surgery. RESULTS: We found morphofunctional alterations only in animals that underwent LLRV in the four periods of sacrifice. The proteinuria creatinine in serum, testosterone in serum and serum corticosterone in serum showed practically no alteration in relation to the normal values for rats. Statistically significant severe histological lesions were found in the kidneys and testes of the LLRV groups. Lesions in the suprarenal glands were also present in these groups, but no sufficient to demonstrate statistical significance. CONCLUSION: Based on these results we can conclude that the ligation of the left renal vein is a procedure of high risk in these animals.     

Pentadecapeptide BPC 157 positively affects both non-steroidal anti-inflammatory agent-induced gastrointestinal lesions and adjuvant arthritis in rats

Besides a superior protection of the pentadecapeptide BPC 157 (an essential fragment of an organoprotective gastric juice peptide BPC) against different gastrointestinal and liver lesions, an acute anti-inflammatory and analgetic activity was also noted. Consequently, its effect on chronic inflammation lesions, such as adjuvant arthritis, and non-steroidal anti-inflammatory agents (NSAIAs)-induced gastrointestinal lesions was simultaneously studied in rats. In gastrointestinal lesions (indomethacin (30 mg/kg s.c.), aspirin (400 mg/kg i.g.) and diclofenac (125 mg/kg i.p.) studies, BPC 157 (10 micrograms or 10 ng/kg i.p.) was regularly given simultaneously and/or 1 h prior to drug application (indomethacin). In the adjuvant arthritis (tail-application of 0.2 mL of Freund's adjuvant) studies (14 days, 30 days, 1 year) BPC 157 (10 micrograms or 10 ng/kg i.p.), it was given as a single application (at 1 h either before or following the application of Freund's adjuvant) or in a once daily regimen (0-14th day, 14-30th day, 14th day-1 year). Given with the investigated NSAIAs, BPC 157 consistently reduced the otherwise prominent lesions in the stomach of the control rats, as well as the lesions in the small intestine in the indomethacin groups. In the adjuvant arthritis studies, the lesion's development seems to be considerably reduced after single pentadecapeptide medication, and even more attenuated in rats daily treated with BPC 157. As a therapy of already established adjuvant arthritis, its salutary effect consistently appeared already after 2 weeks of medication and it could be clearly seen also after 1 year of application. Taking together all these results, the data likely point to a special anti-inflammatory and mucosal integrity protective effect.     

Influence of aging on cortical and trabecular bone response to estradiol treatment in ovariectomized rats

Three groups (n = 15/group) of 6-, 12- and 30-month-old (mature, old and senescent animals, respectively) female Wistar rats on a diet (6 g/100 g BW/ day) containing 0.8% calcium and 0.8% inorganic phosphorus were studied. Within each group, 10 rats were ovariectomized surgically and 5 injected s.c. with 17 beta-estradiol (E rats, 10 micrograms/kg BW/48 h) and 5 with solvent alone (OVX rats) from day 2 until day 60 after ovariectomy. Five other rats were sham-operated (SH rats) and received solvent only. All rats were killed by exsanguination 60 days after ovariectomy. Neither ovariectomy nor estradiol treatment had a significant effect upon tibial mechanical properties in 6-, 12- and 30-month-old animals. Bone mineral density (BMD) and bone mineral content (BMC) of the distal femur and BMC of the whole femur were decreased by ovariectomy in 6- and 12-month-old rats, but were not different in the SH and E groups. In senescent animals, in which the lowest BMD and BMC were measured, estradiol treatment was more effective in increasing these parameters than in adult and old rats. Image analysis of the distal femoral diaphysis showed that estradiol treatment prevented trabecular bone loss induced by senescence and/or ovariectomy. In each group, urinary deoxypyridinoline excretion and plasma osteocalcin concentration were higher in the OVX animals than in the controls, consistent with increased bone turnover in the estrogen-deficient state. Both biochemical turnover markers were reduced in the estrogen-treated groups. These results indicate that 17 beta-estradiol is particularly effective at preventing high-turnover-induced osteopenia in 30-month-old animals.     

Male fertility in rats treated with etretinate for 4 weeks

The toxicity of Etretinate, a retinoid compound, on the male reproductive system was studied in male rats. The drug was administered for four weeks at the dose levels of 0 (control: Vehicle, Peanut oil), 5 and 25 mg/kg/day. The animals were then allowed to mate, and their male reproductive functions and organs were examined in detail. No significant changes due to toxicity were observed in male reproductive functions and organs in the 5 mg/kg/day group after the 4-week treatment. In contrast, males in the 25 mg/kg/day group showed drug-related changes in their reproductive performance (decrease of mating ability and fertility rate), testosterone blood level, sperm head counts, sperm viability and number in the caudal epididymis, organ weight and in the histopathology of their reproductive organs (atrophy of seminiferous tubules, necrosis of spermatocytes and spermatids, vacuolation of nuclei of spermatocytes and spermatids). Even though Etretinate belong to the retinoid group of compounds, the changes seen in the 25 mg/kg/day group were almost the same as those observed in Vitamin A-deficient animals. In conclusion, there is a correlation between changes due to toxicity observed for parameters of male fertility and for histopathological evaluation of the testis of rats that receiving high dose, treatment with Etretinate for 4 weeks.     

Na/H exchange and H-K ATPase increase distal tubule acidification in chronic alkalosis

We examined whether H(+)-ATPase, H(+)-K(+)-ATPase, and or Na+/H+ exchange mediates increased distal tubule acidification in animals with chronic metabolic alkalosis using pharmacological inhibitors of these H+ transporters in in vivo-perfused tubules of anesthetized rats. Chronic metabolic alkalosis was induced with furosemide followed by minimum electrolyte diet and HCO3 drinking water. The reduction in net HCO3 reabsorption was greater in distal tubules of alkalotic compared to control animals perfused with Schering 28080 to inhibit H(+)-K(+)-ATPase (-6.4 +/- 0.9 vs. -1.4 +/- 0.5 pmol/mm.min-1, P < 0.02) and with EIPA to inhibit Na+/H+ exchange (-11.1 +/- 1.7 vs. -6.6 +/- 0.9 pmol/mm.min-1, P < 0.01) but was similar in distal tubules of alkalotic and control animals perfused with bafilomycin to inhibit H(+)-ATPase. The greater reduction of distal tubule net HCO3 reabsorption in alkalotic compared to control animals induced by EIPA was eliminated by systemic infusion of the endothelin receptor antagonist bosentan (-4.6 +/- 0.7 vs. -4.4 +/- 0.7 pmol/mm.min-1, P = NS) but the greater reduction induced by Schering 28080 persisted. Urine endothelin-1 (ET-1) excretion was higher in animals with maintained alkalosis (164.5 +/- 23.7 vs. 76.6 +/- 10.8 fmol/day, P < 0.03), but decreased following KCl repletion to a value (86.7 +/- 10.0 fmol/day, P < 0.02 vs. respective before-KCl value) that was not different from that for KCl-repleted control animals (79.9 +/- 8.7 fmol/day, P = NS vs. KCl-repleted alkalotic animals). The data support that augmented distal tubule acidification in alkalotic animals is due to increased H(+)-K(+)-ATPase and Na+/H+ exchange activity, the latter stimulated by endogenous endothelins.     

Expression of thymidine phosphorylase is associated with a poor prognosis in patients with ductal adenocarcinoma of the pancreas

Adult rats were prepared with either sham or medial prefrontal cortex lesions and administered, beginning on the third post-operative day, either, 0, 40, or 80 mg kg-1 crude ginseng extract suspended in saline daily for the next 30 days. Later, kinetic functions were evaluated on an elevated rotating rod. No long-term influences of the treatments were observed on this task. Significant positive influences of ginseng were observed in the position reversal task. The learning deficits observed in the saline control brain-damaged rats were significantly attenuated in the ginseng-treated animals. An analysis of trial 2 response accuracy across reversals revealed enhanced cognitive abilities (i.e. acquisition of a win-stay, lose-shift strategy) in both the brain damaged and sham control rats administered ginseng. Generally, administration of the higher dose resulted in better performance in the learning paradigm. The exact mechanism responsible for these promising results remains to be discovered. Several possible mechanisms are discussed.     

In vitro study of the effect of miglitol on carbohydrate digestion and intestinal metabolism in normal and non-insulin-dependent diabetic rats

The effect of miglitol was studied (20 mg/kg body weight), administered intraduodenally alone or together with maltose, on the absorption and intestinal metabolism of glucose during its translocation from the lumen of the intestine to the blood, using in vitro perfused preparations of complete small intestine-pancreas, proximal small intestine alone, or distal small intestine alone, isolated from normal and non-insulin-dependent diabetic rats. In the absence of a luminal administration of maltose in normal rats, the glucose uptake from the vascular perfusate was greater in the presence (0.52 +/- 0.04 mmol/h) than in the absence (0.39 +/- 0.02 mmol/h) of miglitol (p < 0.05). In diabetic rats, no significant variations were observed in glucose uptake from the vascular perfusate as an effect of miglitol, but the glucose uptake in the presence of this drug was significantly less (p < 0.05) than that observed in normal rats. Portal lactate was significantly greater (p < 0.05) in diabetic than in normal rats and, after administration of miglitol, rose in both normal and diabetic rats, the rise being significantly greater in normal than in diabetic rats (p < 0.01). When maltose was administered luminally (2 g/kg body weight), the values of portal glucose in both normal and diabetic rats were significantly less in the presence of miglitol in the complete as well as in the distal and proximal small intestine preparations (p < 0.05); the glucose uptake from luminal administered maltose was greater in the presence of miglitol in diabetic (p < 0.05) and in normal (p < 0.05) rats except in the complete small intestine of normal rats; and no significant differences were observed in portal lactate levels between normal and diabetic rats in the presence of miglitol. In conclusion, our results show that miglitol administered luminally at the doses employed here, as well as reducing the transport of glucose from the lumen of the intestine into the blood supply, significantly stimulate intestinal glucose metabolism.     

Membranous modifications in sieve element plasids of spinach affected by the aster yellows disease

Aspirin (ASA), indomethacin (IND), hydrocortisone (HYC) or 0.25% agar (control) were administered (p.o.) daily to rats for 5 days. Following drug pretreatments, the activities of cytosolic superoxide dismutase (SOD), glutathione peroxidase (GP) and glutathione reductase (GR) were elevated 30-70%, 5-25% and 8-25%, respectively. In a second experiment, rats pretreated as above were injected (ip) on the 5th day with paraquat (PQ) (29 mg/kg). Rats in each group expired more ethane 2 hours after PQ injection. After 22 hours, expired ethane returned to zero time levels. All control rats died within 48 hours after PQ injection. At the end of 48 hours, rats pretreated with ASA, IND, or HYC demonstrated survival rates of 13%, 31%, and 47%, respectively. PQ injection produces marked elevations of SOD (82%), GP (328%), and GR (36%) in the lungs of PQ-injected controls rats over non-PQ injected controls. Elevation of these enzymes were also noted in drug-treated rats after PQ injection but at values less than PQ-injected controls. Anti-inflammatory drugs were tested in rat liver homogenates for their ability to inhibit thiobarbituric acid (TBA) reactive product formation. Only the addition of HYC resulted in a decrease formation of TBA-reactive products. Thus in vitro studies suggest that the antiinflammatory drugs tested, other than HYC, may have other mechanisms of actions in addition to inhibition of lipid peroxides.     

Hydrocortisone induces an increase of amylase content in individual zymogen granules from rat pancreas

This study was performed to evaluate the effects of different doses of hydrocortisone (1, 10 and 25 mg/kg/day) administered for 1, 3 and 8 days on pancreatic enzyme storage in rats. The enzyme content in both pancreas homogenates and in individual isolated zymogen granules (ZGs) was measured using standard biochemical assays and flow cytometry, respectively. Hydrocortisone did not alter the total amount of pancreatic DNA but increased the pancreas enzyme content in a time-dose-dependent way. Amylase activity was significantly increased after hydrocortisone administration at day +8 when 10 mg/kg/day was used, and from the first day of treatment when 25 mg/kg/day was administered. A significant increase in trypsin activity was also observed in response to 25 mg/kg/day of hydrocortisone but only from the third day of treatment onwards. As compared with control rats, chronic administration of either 1 or 10 mg/kg/day of hydrocortisone did not alter significantly either the size or the percentage of the two ZG subpopulations (Z1 and Z2) identified in the pancreas by flow cytometry; in addition, no significant changes were observed in the mean amylase content per individual granule, although its mean concentration increased in rats treated with 10 mg/kg/day for 3 and 8 days. Nevertheless, when 25 mg/kg/day of hydrocortisone were administered for 1 and 3 days, a significant increase in the proportion of Z1 ZGs was observed, which may be related to the formation of new and smaller ZGs. When a very high dose of hydrocortisone (25 mg/kg/day) was used, an overall increase in the pancreatic enzyme content related to an increase in the mean amylase content per individual ZG was observed; this effect was apparent from the first day of treatment in the Z1 subset of ZGs and from day +3 in the Z2 subpopulation. Only a high concentration of hydrocortisone was able to alter the enzyme storage process in individual zymogen granules, but they maintain a normal enzyme load at lower hydrocortisone doses.     

Influence of ovariectomy on bone metabolism in very old rats

Twenty-five 30-month-old Lou rats fed a diet (6 g/100 g BW/day) containing 0.9% Ca and 0.8% Pi were divided into five groups. Four groups were surgically ovariectomized. From day 2 until day 29 after ovariectomy, they were S.C. injected either with 17 beta estradiol (E2; 10 micrograms/kg BW/48 hours) or progesterone (P; 140 micrograms/kg BW/48 hours), or 17 beta estradiol + progesterone (E2P) at the same doses, or solvent alone (OVX). The fifth group was sham operated (SH) and injected with solvent. Urine was collected in metabolic cages from day 24 to 29 after ovx, and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) excretion (markers of bone resorption) was measured by HPLC. All animals were killed 30 days after ovariectomy. Serum was then collected for measurement of osteocalcin (OC), alkaline phosphatase (ALP), parathyroid hormone (PTH), and calcitonin (CT). At necropsy, the success of ovariectomy was checked by marked atrophy of the uterine horns. Left and right femur were harvested for densitometric and mineral analysis, respectively. Ovariectomy had no significant effect upon plasma calcium and PTH concentrations. E2 or E2P treatment significantly increased plasma PTH and calcitonin concentrations. Plasma OC concentrations and ALP were not different in any of the groups. In contrast, urinary excretion of PYD and DPD was higher in OVX than in SH rats. Bone mineral density (BMD) of the distal femur was decreased by OVX, but was not different in the E2P and SH groups. A similar pattern was observed for the mineral or Ca content of whole femur. Thus, OVX decreased BMD and bone mineral content (BMC) in very old female rats. Plasma OC concentration and ALP activity failed to demonstrate any significant effect of OVX, whereas PYD and DPD were elevated. These results suggest that bone resorption is increased in OVX rats, even when supplemented with E2 or P alone. However, no significant difference was observed between SH and OVX rats treated with supplementation of both E2 and P. Thus, in very old rats, a combination of E2 and P is much more effective than E2 or P alone to prevent bone loss following ovariectomy.