Disposition of procainamide and N-acetylprocainamide in protein-calorie malnutrition

The influence of dietary protein deficiency on the disposition of procainamide (PA) and its major metabolite, N-acetylprocainamide (NAPA) was investigated in male Sprague-Dawley rats fed for 4 weeks on a 23 (control) or a 5% (low) protein diet ad libitum. Procainamide and N-acetylprocainamide in plasma and urine were determined by a sensitive and specific HPLC assay using a cation-exchange column. After an iv dose of 50 mg/kg procainamide hydrochloride, the average mean residence time (MRT) was approximately 82% higher, while the total plasma clearance (CI) per kg of body weight and terminal elimination rate constant (k) were significantly decreased by 46 and 49%, respectively, in the protein-deficient animals. No significant differences were found in the two groups of animals with respect to the apparent steady state volume of distribution (Vss). Although the percentage of PA recovered unchanged in the urine over 48 hr was not significantly different between control and protein-deficient animals, rats on a low protein diet excreted a smaller percentage of the administered PA dose (mean +/- SE, 19.0 +/- 4.0 vs. 30.8 +/- 1.4%) as NAPA. In addition to the apparent decrease in metabolic clearance (CIm) to NAPA (6.8 +/- 1.4 vs. 19.9 +/- 2.3 ml/min/kg) in the protein-deficient rats, there was a 55% decrease in the renal clearance of PA. There appeared to be no significant difference in the disposition characteristics of NAPA (i.e. MRT, Vss, CI, and k) between the two groups of animals after a 25 mg/kg dose of N-acetylprocainamide hydrochloride.(ABSTRACT TRUNCATED AT 250 WORDS)     

Absorption and disposition kinetics of chlorothiazide in protein-calorie malnutrition

The influence of dietary protein deficiency on the absorption and disposition kinetics of chlorothiazide was investigated in male Sprague-Dawley rats fed for 4 weeks on a 23 per cent (control) or a 5 per cent (low) protein diet ad libitum. Chlorothiazide in plasma and urine was determined by a sensitive and specific HPLC assay. Following an intravenous dose of 10 mg kg-1 chlorothiazide, there was a significant decrease in the total plasma clearance (Cl) per kg of body weight from 1.80 +/- 0.15 to 1.29 +/- 0.15 l h-1 kg-1 and apparent steady-state volume of distribution from 0.65 +/- 0.13 to 0.38 +/- 0.07 l kg-1 in the protein-deficient rats. However, no significant difference was found in the two groups of animals with respect to mean residence time (MRT) and free fraction of drug in plasma. The mean harmonic half-life was increased from 72 to 91 min in the protein-deficient rats. The urinary recovery of unchanged chlorothiazide in 48 h was essentially complete in both groups of animals. The absorption of chlorothiazide, as assessed by the mean urinary recovery of unchanged drug after oral administration, was 66 per cent and 68 per cent in normal and protein-deficient rats, respectively.     

Influence of Malnutrition on the Disposition of Metronidazole in Rats

The influence of dietary protein deficiency on the disposition of metronidazole and its two major metabolites was examined in male Sprague–Dawley rats fed for 4 weeks on a 23% (control-) or a 5% (low-) protein diet ad libitum. Following an intravenous bolus dose of 10 mg/kg metronidazole hydrochloride, blood samples were obtained serially for a period of 24 hr after drug administration. Serum concentration–time data were analyzed by nonlinear least-squares regression, as well as noncompartmental techniques. The average mean residence time (MRT) was significantly prolonged by 48%, while the systemic clearance (Cl) was decreased by 42% in the protein-deficient rats. Since there was no alteration in the apparent steady-state volume of distribution (V _ss), the mean harmonic half-life was increased from 2.9 to 5.0 hr in the protein-deficient rats. Although the percentage of metronidazole recovered as total drug in the urine over 24 hr was not significantly different between the two groups of animals, rats on a low-protein diet excreted a significantly smaller percentage of the administered dose as unchanged metronidazole (mean ± SD, 24.6 ± 3.8 vs 36.5 ± 12%) and a larger percentage (16.7 ± 2.6 vs 8.3 ± 1.8%) as the hydroxylated metabolite. No significant difference in the partial metabolic clearance of the hydroxylated metabolite of metronidazole was seen between the two groups of animals; however, there was a significant decrease in the renal clearance of metronidazole (1.45 ± 0.68 vs 0.55 ± 0.06 ml/min/kg) in the rats fed a low-protein diet. We conclude that the decreased clearance of metronidazole in protein deficiency is a result primarily of the decreased glomerular filtration rate, decreased biliary excretion, and/or increased net tubular reabsorption of metronidazole.     

Pharmacokinetics, metabolism and disposition of salicylate in protein-deficient rats

The influence of dietary protein deficiency on the pharmacokinetics, metabolism, and disposition of sodium salicylate was investigated in Sprague-Dawley male rats. Animals were fed for 3 weeks a 21% (control) or a 5% (deficient) protein diet ad lib.; an additional group of rats (pair-fed controls) was fed for 3 weeks the control 21% protein diet in a restricted quantity (10 g/day/rat), which was approximately equal to the quantity (9.8 g/day) consumed by rats receiving the 5% protein diet ad lib. Sodium salicylate (in salicyclic acid equivalents) and its metabolites were assayed by HPLC. In both control and protein-deficient rats, sodium salicylate kinetics were dose-dependent and the decline in its plasma concentration proceeded according to a first-order process; no differences in the two groups of animals were found with respect to the following features of the biological fate of salicylate: plasma half-life and clearance at a 2-mg/kg (iv) dose level, volume of distribution at all dose levels (2, 10, and 100 mg/kg, iv), relative bioavailability by oral route, tissue distribution, and the rate of urinary excretion of salicyl glucuronides at 10-mg/kg dose level. However, at high dose levels (10 and 100 mg/kg, iv), the plasma half-life of salicylate was shorter and its clearance greater in protein-deficient than in control rats. The following additional changes were caused by dietary protein deficiency: a decrease in salicylate binding to serum protein, an increase in the metabolic transformation of salicylic acid to its glycine conjugate, salicyluric acid, by kidney mitochondrial preparations, an increase in the urinary excretion of salicyluric acid and salicylic acid, and a decrease in the elimination half-life of salicylic acid; the excretion of salicyluric acid proceeded according to a first-order process in protein-deficient rats but according to an apparent zero-order process in the controls. The changes in the plasma half-life and clearance of salicylate in pair-fed controls were not significant; it appears that a deficiency of both proteins and calories (protein-deficient rats) exerts greater influence on the biological fate of salicylate than does a deficiency mainly of calories (pair-fed controls). It is suggested that the decrease in the plasma half-life of salicylate in protein-deficient rats is the result of an increase in its clearance, which in turn is caused by a decrease in protein-salicylate binding and an increase in the metabolism of salicylic acid to salicyluric acid. These results point to the desirability of a systematic study of the biological fate of salicylate during clinical malnutrition, which is common in developing countries.     

Inhibition and induction of theophylline metabolism by 8-methoxypsoralen. In vivo study in rats and humans

The effects of 8-methoxypsoralen (8-MOP) on the metabolism of theophylline were studied in rats and humans. Rats were randomized into three groups and prepared with iv jugular catheters. Group I (N = 4) received a single ip injection of 27 mg/kg of 8-MOP, group II (N = 5) vehicle (corn oil), and group III (N = 4) 50 mg/kg/day of 8-MOP for 3 days. Rats were subsequently administered 15 mg/kg of theophylline iv, and timed blood samples (0.2 ml) were assayed for theophylline by HPLC. Theophylline clearance (ml/min/kg; mean +/- SD) was 1.7 +/- 0.3, 2.4 +/- 0.5, and 9.5 +/- 1.6 in groups I, II, and III, respectively. The half-life (harmonic mean) from 0.5 to 12 hr was 7.2, 3.6, and 0.8 hr. Urinary excretion of unchanged theophylline (mean +/- SD) from 0 to 24 hr was 60 +/- 10, 41 +/- 6, and 13 +/- 3% of the administered dose. In a crossover study, three healthy, male, nonsmokers received 600 mg of oral theophylline. Urine and plasma were collected for 48 hr. One week later, subjects received 1.2 mg/kg of oral 8-MOP followed in 1 hr by 600 mg of oral theophylline. Mean residence time of theophylline increased from 10.7, 17.2, and 12.2 hr in the control period, to 20.3, 19.0, and 18.4 hr after 8-MOP. The AUC (microgram.hr/ml) of theophylline increased from 204, 213, and 204, to 555, 364, and 432, while clearance (ml/min/kg) decreased from 0.74, 0.57 and 0.63, to 0.27, 0.33, and 0.30, respectively. Urinary excretion of unchanged theophylline from 0 to 48 hr increased from 14, 14, and 15, to 24, 21, and 20%. We conclude that 8-MOP administered acutely is a potent inhibitor of theophylline metabolism and chronically in the rat is a powerful inducer.     

The influence of maternal protein deficiency on the placental transfer of salicylate in rats.

1 The influence of a low protein diet (5% as compared with a control 21% protein diet) on the placental transfer of sodium salicylate was investigated in Sprague-Dawley rats on day 20 of gestation. 2 Maternal plasma salicylate concentrations (assayed by high pressure liquid chromatography) were generally lower in protein-deficient than in control animals at a wide range of times (0.25 - 12 h) and dose levels (2 - 250 mg/kg, i.v.); however, foetal plasma salicylate levels in the two groups of animals did not differ. 3 The placental transfer of salicylate as indicated by the ratio of foetal plasma or foetal liver to maternal plasma salicylic acid concentration was consistently and significantly greater in the protein-deficient group than in the control group of animals following the administration of the drug to the mother as well as to the foetus. 4 A decrease in calorie without a concomitant decrease in protein intake (pair-fed controls) did not alter the placental transfer of salicylate. 5 The increased placental transfer of salicylate in protein-deficient animals could not be attributed to changes in serum protein-salicylate binding. 6 It is suggested that the pharmacokinetic factors responsible for maintaining a lower level of salicylate in the foetus than in the mother are impaired by maternal malnutrition, and this may increase the foetal effects of maternally ingested salicylate.     

Hepatoprotective Role of Zinc in Lead-Treated,Protein-Deficient Rats

The current study was designed to evaluate the hepatoprotective role of zinc after lead (Pb) treatment of protein-deficient (PD) rats. The animals were subjected to seven different treatment groups: G-1 (normal control, 18% protein), G-2 (protein-deficient, 8% protein), G-3 (Pb-treated, 100 mg/kg body weight of lead acetate), G-4 (Zn-treated, zinc sulfate at a dose level of 227 mg/L drinking water), G-5 (PD + Pb-treated), G-6 (PD + Zn-treated), and G-7 (PD + Pb + Zn-treated). Serum albumin levels and total serum protein contents were estimated to assess the severity of protein deficiency at the end of 8 weeks in all the treatment groups. Also, the study explored the role of zinc on antioxidative defense system enzymes in liver of protein-deficient rats subjected to lead toxicity treatment. Further, the study was extended to elucidate the levels of zinc and lead in liver tissue after different treatments of rats using positron-induced X-ray emission technique (PIXE). The current study indicated a significant change in the levels of various antioxidative enzymes and serum albumin as well as total protein contents of protein-deficient rats subjected to lead treatment. A significant increase in the levels of malondialdehyde (MDA), catalase, and glutathione peroxidase (GPx) was seen after 8 weeks of lead treatment of protein-deficient rats. On the contrary, levels of albumin, total protein content, superoxide dismutase (SOD), GSH, were found to be decreased. Interestingly, zinc supplementation has tended to normalize the altered levels of these enzymes to a significant extent. The levels of zinc in liver tissue was found to be decreased significantly in protein-deficient as well as lead-treated rats. However, hepatic zinc concentration was increased to a significant extent in protein-deficient rats supplemented with zinc when compared with protein-deficient rats. Further, the presence of lead was also observed in livers of lead-treated animals. In conclusion, the study revealed the antioxidative role of zinc in hepatotoxic conditions induced by subjecting the rats to protein-deficient diet and lead treatment.     

Azotemia during chronic converting enzyme inhibition with enalapril in sodium-depleted rats: role of renal circulatory changes

Chronic administration of the angiotensin-converting enzyme inhibitor enalapril to sodium-restricted rats causes azotemia and elevations in serum creatinine. This study was undertaken to determine the contribution of altered systemic and renal hemodynamics to the reductions in renal function in sodium-restricted rats treated with enalapril. Animals were maintained for 21 days on a sodium-restricted diet (0.04 +/- 0.01 mEq Na+/24 h). Enalapril was administered in the drinking water (300 mg/L) to half the rats. Regional blood flows were measured in animals anesthetized with pentobarbital (50 mg/kg, i.p.) using the radioactive microsphere technique. Converting enzyme inhibition (CEI) reduced mean arterial pressure (130.8 +/- 5.9 vs 60.3 +/- 6.1 mm Hg, p less than 0.001), and increased cardiac index (346 +/- 33 vs. 437 +/- 28 ml/min/kg, p less than 0.05). Total peripheral resistance was significantly lower in enalapril-treated rats [0.406 +/- 0.049 vs. 0.166 +/- 0.013 arbitrary resistance units (RU), p less than 0.001]. Renal blood flow was maintained (control, 2.93 +/- 0.21 vs. enalapril, 2.55 +/- 0.28 ml/min/100 g, p = NS) despite a 54% decrease in perfusion pressure due to decreased renal vascular resistance (42.6 +/- 1.7 vs. 25.2 +/- 2.9 RU, p less than 0.001). CEI reduced coronary blood flow (2.76 +/- 0.22 vs. 1.59 +/- 0.19 ml/min/100 g, p less than 0.001), but did not change coronary vascular resistance (50.2 +/- 4.6 vs. 44.0 +/- 4.3 RU, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)     

Hepatoprotective role of zinc in lead-treated, protein-deficient rats

The current study was designed to evaluate the hepatoprotective role of zinc after lead (Pb) treatment of protein-deficient (PD) rats. The animals were subjected to seven different treatment groups: G-1 (normal control, 18% protein), G-2 (protein-deficient, 8% protein), G-3 (Pb-treated, 100 mg/kg body weight of lead acetate), G-4 (Zn-treated, zinc sulfate at a dose level of 227 mg/L drinking water), G-5 (PD + Pb-treated), G-6 (PD + Zn-treated), and G-7 (PD + Pb + Zn-treated). Serum albumin levels and total serum protein contents were estimated to assess the severity of protein deficiency at the end of 8 weeks in all the treatment groups. Also, the study explored the role of zinc on antioxidative defense system enzymes in liver of protein-deficient rats subjected to lead toxicity treatment. Further, the study was extended to elucidate the levels of zinc and lead in liver tissue after different treatments of rats using positron-induced X-ray emission technique (PIXE). The current study indicated a significant change in the levels of various antioxidative enzymes and serum albumin as well as total protein contents of protein-deficient rats subjected to lead treatment. A significant increase in the levels of malondialdehyde (MDA), catalase, and glutathione peroxidase (GPx) was seen after 8 weeks of lead treatment of protein-deficient rats. On the contrary, levels of albumin, total protein content, superoxide dismutase (SOD), GSH, were found to be decreased. Interestingly, zinc supplementation has tended to normalize the altered levels of these enzymes to a significant extent. The levels of zinc in liver tissue was found to be decreased significantly in protein-deficient as well as lead-treated rats. However, hepatic zinc concentration was increased to a significant extent in protein-deficient rats supplemented with zinc when compared with protein-deficient rats. Further, the presence of lead was also observed in livers of lead-treated animals. In conclusion, the study revealed the antioxidative role of zinc in hepatotoxic conditions induced by subjecting the rats to protein-deficient diet and lead treatment.     

Disposition of (5H-dibenzo [a,d]cyclohepten-5-ylidene)acetic acid in laboratory animals

The disposition of (5H-dibenzo[a,d]cyclohepten-5-ylidene)acetic acid (Wy-41,770), an anti-inflammatory agent, was investigated in rats, mice, rhesus monkeys, and dogs following single 12.5-mg/kg doses of 14C-labeled or unlabeled drug and in rodents receiving single 225-mg/kg doses of 14C-Wy-41,770. The drug was rapidly and well absorbed in all four animal species. Following an iv dose, plasma elimination half-lives of Wy-41,770 in monkeys and dogs were, respectively, 5.0 +/- 1.8 and 0.24 +/- 0.01 hr. Total body clearances (CL) of 1.8 +/- 0.2 ml/min/kg in monkeys and 7.7 +/- 1.1 ml/min/kg in dogs are low, indicating that, after an ig dose, little Wy-41,770 would be eliminated on first passage through the liver. The steady state volumes of distribution of 0.37 +/- 0.1 and 0.14 +/- 0.01 liters/kg, respectively, in monkeys and dogs are low, indicating limited extravascular distribution of Wy-41,770. Plasma half-lives of Wy-41,770 in rats and mice were, respectively, 10.8 and 8.4 hr. The longer half-life in rats compared to other animals is due to the extensive enterohepatic recycling of the drug in rats. The extensive cycling of the drug in rats may explain why ileocecal inflammation occurred in this species but not in mice and dogs following prolonged oral administration of high doses of Wy-41,770. Following a 12.5 mg/kg, ig dose, the rates of urinary excretion of radioactivity in monkeys, mice, and rats were, respectively, 73.4 +/- 10.7, 52.6 and 15.2% of the dose, whereas the fecal excretion was 9.1 +/- 3.7% in monkeys and 74.7% in rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute effects of pentobarbital-anaesthesia on bile secretion

Male Wistar rats were equipped with permanent catheters in the bile duct and the duodenum under ether anaesthesia, at least seven days before the experiments. By this technique, the enterohepatic circulation can be interrupted for bile collection without direct surgical intervention. 14C-Pentobarbital (26.6 mumole/100 g body wt) was injected intraperitoneally immediately before interruption of the enterohepatic circulation (NBD, Non-Bile Diverted) or after eight days of bile diversion (BD, Bile Diverted). In NBD rats, bile flow and biliary bile acid excretion were significantly reduced during the first hour after pentobarbital administration when compared to unanaesthetized controls, but markedly increased thereafter. Pentobarbital treatment slightly decreased biliary bile acid excretion in BD rats, but caused a 60% increase in bile flow. Within four hours 22.3 +/- 0.4% and 26.0 +/- 2.7% of the injected radioactivity was excreted into bile in NBD and BD rats, respectively. The calculated osmotic activity of pentobarbital and its metabolites was 47.8 +/- 5.2 microliter/mumole in NBD rats and 37.8 +/- 1.3 microliter/mumole in BD rats. Consequently, pentobarbital treatment affected the bile acid independent fraction of bile flow (BAIF). The calculated BAIF was 2.68 microliter/min/100 g body wt in unanaesthetized animals, but 4.27 microliter/min/100 g body wt in pentobarbital treated NBD rats. Corresponding values for BD rats were 1.70 and 2.38 microliter/min/100 g body wt. It is concluded that pentobarbital anaesthesia affects bile production in the rat by direct and indirect means. Firstly, pentobarbital and its metabolites are rapidly excreted into bile and exert a significant choleretic effect, thereby increasing the BAIF. Secondly, pentobarbital anaesthesia retards the exhaustion of the intestinal bile acid pool, which leads to secondary changes in the biliary excretion process.     

Pharmacokinetics of theophylline in protein-calorie malnutrition

The influence of protein-calorie malnutrition (PCM) on the disposition of theophylline was investigated in male Sprague-Dawley rats fed for four weeks on a 23 per cent (control) or 5 per cent (low) protein diet ad lib. Dietary protein deficiency led to a decrease in body weight gain, plasma proteins, albumin, microsomal proteins, and cytochrome P-450. After intravenous administration of aminophylline equivalent to 10 mg kg-1 theophylline, the average mean residence time (MRT) was 58 per cent higher in the protein-deficient rats, while the total plasma clearance (Cl) per kilogram of body weight and elimination rate constant (k) were decreased by 39 per cent and 45 per cent, respectively, when compared to rats on a normal protein diet. No significant difference was found in the two groups of animals with respect to the apparent steady-state volume of distribution (Vss). The present results suggest that the mechanism responsible for the observed pharmacokinetic changes in the protein-deficient rats is related to the reduced amount and/or activity of the hepatic mixed function oxidases.     

Bioavailability and mammary excretion of bisphenol a in Sprague-Dawley rats.

This study reports the absolute oral bioavailability and mammary excretion of bisphenol A in rats. The oral bioavailability was determined after administration of relatively low iv (0.1 mg/kg) and oral (10 mg/kg) doses of bisphenol A to rats. After iv injection, serum levels of bisphenol A declined biexponentially, with the mean initial distribution and terminal elimination half-lives being 6.1 +/- 1.3 min and 52.5 +/- 2.4 min, respectively. The systemic clearance (Cls) and the steady-state volume of distribution (Vss) averaged 107.9 +/- 28.7 m/min/kg and 5.6 +/- 2.4 L/kg, respectively. Upon oral administration, the maximum serum concentration (Cmax) and the time to reach the maximum concentration (Tmax) were 14.7 +/- 10.9 ng/ml and 0.2 +/- 0.2 h, respectively. The apparent terminal elimination half-life of bisphenol A (21.3 +/- 7.4 h) after oral administration was significantly longer than that after iv injection, indicating the flip-flop of the absorption and elimination rates. The absolute oral bioavailability of bisphenol A was low (5.3 +/- 2.1%). To determine the extent of mammary excretion, bisphenol A was given by simultaneous iv bolus injection plus infusion to steady state at low, medium, and high doses. The steady-state serum levels of bisphenol A were linearly increased with higher dosing rates. The systemic clearance (mean range, 119.2-154.1 ml/min/kg) remained unaltered over the dosing rate studied. The levels of bisphenol A in milk exceeded those in serum, with the steady-state milk to serum concentration ratio being 2.4-2.7.     

Comparative pharmacokinetics of coumarin anticoagulants XLIII: Concentration-dependent hepatic uptake of warfarin in rats

The purpose of this study was to determine if hepatic warfarin uptake, which has a major quantitative effect on warfarin distribution in rats, is concentration dependent. Adult male rats received either 0.1 or 1.0 mg of racemic warfarin/kg iv and were killed 6 hr later. With increasing dose, the concentrations of free and total (free plus protein-bound) serum warfarin increased much more than proportionally, and the total warfarin concentration in the liver increased much less than proportionally. The liver to serum total warfarin concentration ratios 6 hr after injection of the 0.1- and 1.0-mg/kg doses were 11.3 +/- 1.7 and 0.814 +/- 0.222, respectively (mean +/- SD, n = 6, p less than 0.001). The ratio of the total drug concentration in the liver to the free drug concentration in serum (mean +/- SD) was 866 +/- 105 in animals that received the 0.1-mg/kg dose and 111 +/- 42 in animals that received the 1.0-mg/kg dose (p less than 0.001). It is concluded that hepatic warfarin uptake decreases with increasing drug concentration and that this may cause the apparent volume of distribution of warfarin to decrease with increasing dose in rats.     

Kinetics of drug action in disease states. XXXVI: Effect of cyclosporine on the pharmacodynamics and pharmacokinetics of a barbiturate (heptabarbital) in rats

Pretreatment with cyclosporine reportedly prolongs the effect of certain general anesthetics in humans and the sleeping time of mice after pentobarbital administration. This investigation was designed to determine the mechanism(s) of the cyclosporine-barbiturate interaction. Adult female Wistar rats received cyclosporine (50 mg/kg im) or saline solution daily for 3 days. On the third day, they were injected with heptabarbital (45 mg/kg iv). Other cyclosporine-treated and control groups were infused with heptabarbital until they lost their righting reflex. Treatment for 3 d with cyclosporine was associated with decreased rectal temperature, decreased magnesium concentrations in serum and CSF, increased serum creatinine and urea nitrogen concentrations, elevated serum aspartate aminotransferase activity and total bilirubin concentration, decreased serum total protein concentration, and increased hematocrit. These physiologic changes are consistent with the clinically observed hypomagnesemia, nephrotoxicity, and hepatotoxicity in patients treated with cyclosporine. Control rats slept for 90 +/- 14 min (mean +/- SD, n = 9) after heptabarbital injection, whereas cyclosporine-pretreated rats slept for 154 +/- 22 min. Compared with controls, cyclosporine-pretreated rats awoke (after heptabarbital injection) and went to sleep (after heptabarbital infusion) with significantly lower barbiturate concentrations in serum and CSF. Pretreatment with a single 60-mg/kg im dose of cyclosporine 2 h before heptabarbital infusion caused no significant biochemical changes approximately 160 min later, except for elevated serum aspartate aminotransferase (which occurred also after injection of the surfactant-containing vehicle) and serum bilirubin. Again, heptabarbital concentrations at onset of sleep (loss of righting reflex) in serum, brain, and CSF of cyclosporine-treated rats were significantly lower than in saline-treated controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of protein-deficient nutrition during rat pregnancy and development on developmental hindlimb crossing due to methylmercury intoxication

Pregnant rats were fed either a control (20% protein) or low (3.5%) protein diet during gestation and lactation. The pups were separated from their mothers on postnatal day 21, and were given the same diet as their corresponding mothers. The groups of pups from each diet group were treated on either postnatal day 21 or postnatal day 60 with 7.5 mg methylmercury chloride (MeHgCl) per kg b.w. once daily by gavage for 10 consecutive days, and the development of ataxia (hind-limb crossing) was monitored. The offspring from mothers on the protein-deficient diet were found to be more sensitive to MeHg-induced ataxia than those on the protein-sufficient diet. The former accumulated more mercury in different brain regions than the latter. The rates of protein synthesis in different brain regions of the offspring fed the protein-deficient diet were significantly reduced compared with the rates in those fed the protein-sufficient diet. However, MeHg treatment did not significantly modify the rates of such protein synthesis further in protein-deficient rats. Thus, a significantly much higher inhibition of the intrinsic rates of protein synthesis in different brain regions due to severe protein deficiency, as observed in this study, may be partly responsible for the increased susceptibility of developing rats fed a protein-deficient diet to MeHg-induced ataxia, or hindlimb crossing, although other factor(s) might also be involved.     

Alterations in synaptic membrane molecular order associated with alcoholization and protein deficiency in rats

The effects of chronic alcoholization and protein deficiency on synaptic membrane characteristics were studied in rats fed the following four liquid diets for 4 weeks: a protein-deficient diet containing alcohol, a protein-deficient diet containing no alcohol, a non-protein-deficient diet containing alcohol and a non-protein-deficient diet containing no alcohol. A fluorescent probe, diphenylhexatriene (DPH), was used to estimate the fluidity of synaptic membranes and their sensitivity to the fluidizing effect of ethanol added in vitro, in concentrations ranging from 50 mM to 800 mM. Prior to in vitro addition of ethanol, the difference between the fluidity of synaptic membranes of alcoholized and non-alcoholized animals was significant for the two groups of protein-deficient animals but not for the two groups of non-protein-deficient animals. After in vitro addition of ethanol, the differences between the fluidity of synaptic membranes of the alcoholized and non-alcoholized animals were larger and more frequently significant for the protein-deficient animals than for the non-protein-deficient animals. In view of previous observations that rats fed a protein-deficient diet experience more severe withdrawal symptoms following alcoholization than rats fed a nutritionally adequate diet, the results of the present experiment lend additional support to the hypothesis that tolerance and dependence may be mediated by alterations in biomembrane characteristics.     

Effect of medroxyprogesterone acetate on hepatic lipid profile of female rats under various states of nutrition

The effect of medroxyprogesterone acetate (MPA) treatment on hepatic lipid profile was studied in female rats kept on protein-deficient diet, on normal restricted diet and on normal, ad libitum diet. A significant decline in total and free cholesterol levels was observed in rats kept on protein-deficient diet and on normal, restricted diet. However, protein-deficient animals exhibited a significant rise in the liver triglyceride level. In rats on normal, ad libitum diet only, MPA treatment resulted in elevated levels of triglycerides and increased esterification of cholesterol. This was mostly due to increased incorporation of acetate into esterified cholesterol and triglyceride as evident from studies using the labelled precursor. Total phospholipid content was found to be unaffected by MPA in all the groups suggesting that the drug and dietary protein level have no effect on hepatic phospholipid content.     

The myocardial infarct size-limiting and antiarrhythmic effects of acyl-CoA:cholesterol acyltransferase inhibitor VULM 1457 protect the hearts of diabetic-hypercholesterolaemic rats against ischaemia/reperfusion injury both in vitro and in vivo

The study was designed to characterise the influence of a novel acyl-CoA:cholesterol acyltransferase inhibitor, VULM 1457, on the severity of myocardial ischaemia-reperfusion injury in a model of diabetes mellitus and hypercholesterolaemia induced by co-administration of streptozotocin and a high fat-cholesterol diet. We used Langendorff-perfused rat hearts to measure the size of myocardial infarction after 30 min of regional ischaemia, followed by a 2-h reperfusion period, and open-chest rats were exposed to 6 min of ischaemia and 10 min of reperfusion to analyse ventricular arrhythmias. In addition to the high fat-cholesterol diet, VULM 1457 was administered to the diabetic-hypercholesterolaemic rats for 5 days. Decreased plasma and liver cholesterol levels and a significantly reduced occurrence of ventricular fibrillation (29% vs. 100%, P<0.01), determined via the mean number and duration of episodes (0.6+/-0.4 and 2.1+/-1.4 s vs. 2.8+/-0.8 and 53.5+/-14.4 s in diabetic-hypercholesterolaemic rats, both P<0.01), were observed in these animals. Lethal ventricular fibrillation was suppressed, and arrhythmia severity was also significantly decreased in these animals as compared to the non-treated animals (2.9+/-0.6 vs. 4.9+/-0.2; P<0.05). A smaller infarct size, normalised to the size of area at risk, was observed in the treated diabetic-hypercholesterolaemic group as compared to the non-treated group (16.3+/-1.9% vs. 37.3+/-3.1%; P<0.01). Aside from remarkable hypolipidaemic activity, VULM 1457 improved the overall myocardial ischaemia-reperfusion injury outcomes in the diabetic-hypercholesterolaemic rats by suppressing arrhythmogenesis as well as by reducing myocardial necrosis.     

Calcium ethylenediaminetetraacetate (CaEDTA) toxicity: studies on the mechanism of CaEDTA potentiation of pentobarbital anesthesia in the rat.

Rats which received an iv infusion of CaEDTA (6 mmol/kg/24 hr for 36 and 48 hr) were more susceptible to the anesthetic effect of pentobarbital Na than rats similarly infused with 0.9% NaCl solution. Less mg/kg pentobarbital Na, administered iv, were required to induce a state of surgical anesthesia. The data indicated that the potentiative action of CaEDTA probably was due to an effect on central neurones rather than enhanced distribution of the anesthetic to the brain. This contention was based upon the following findings in CaEDTA-treated rats relative to controls: lower pentobarbital concentrations in the brain at the onset of anesthesia, no difference in brain/plasma concentration ratios of anesthetic when appropriate corrections were made for binding to plasma proteins and pH-pK_A relationships in blood, and no difference in brain/plasma concentration ratios of a normally nonpermeating solute. Moreover, when standard doses of pentobarbital Na were given ip, CaEDTA-treated rats slept significantly longer and concentrations of pentobarbital in plasma and brain were significantly less than controls on arousal. Dexamethasone antagonized the potentiative effect of CaEDTA on pentobarbital anesthesia. The occurrence of higher concentrations of pentobarbital in brain and a lower brain/plasma concentration ratio at the onset of anesthesia suggested the steroid acted to stabilize cerebral neurones to the effect of the anesthetic as well as impede the distribution of pentobarbital to the brain. Serotonin concentrations were found to be significantly decreased in brain, duodenum, and kidney, but not the liver, consequent to CaEDTA administration. The iv infusion of calcium acetate, equimolar to CaEDTA, also potentiated barbiturate anesthesia.