Application of serial sampling of cerebrospinal fluid in pharmacodynamic studies with a drug active in the CNS: heptabarbital concentrations at onset and offset of loss of righting reflex in rats

As cerebrospinal fluid (CSF) possesses unique characteristics in order to explore concentration-pharmacological response relationships of drugs active in the CNS, the practicability of serial sampling of CSF was tested in a study with heptabarbital. Concentrations in CSF and plasma were measured simultaneously in individual rats during and after an intravenous infusion for 30 min. At the end of the infusion, the distribution equilibrium was attained with a CSF/plasma concentration ratio of 0.38, roughly equal to the fraction unbound to protein. When concentrations in blood and CSF were determined at the onset and offset of loss of righting reflex concentrations in blood were significantly greater at onset (146 +/- 19 mg/l) than at offset (108 +/- 16 mg/l, n = 6), whereas concentrations in CSF were identical (39 +/- 5 and 38 +/- 5 mg/l, respectively). This confirmed the earlier observation that the CSF is pharmacokinetically indistinguishable from the site of action. When the duration of the loss of righting reflex was varied, concentrations of heptabarbital in CSF at onset and offset were similar, independent of the duration of the loss of righting reflex (1-5 hr). These findings demonstrate the absence of the development of acute tolerance and confirmed that no (inter)active metabolites interfered with the pharmacological response. In a total number of 26 rats the concentrations in CSF at onset and offset of loss of the righting reflex were compared. The interindividual variation was 13-15% and the intra-individual variation was only 4-6%. The results demonstrate the usefulness of serial sampling of CSF in pharmacodynamic studies with centrally acting drugs.     

Strategy to assess the role of (inter)active metabolites in pharmacodynamic studies in-vivo: a model study with heptabarbital

The purpose of this investigation was to develop a universal experimental strategy by which the role of (inter)active metabolites in in-vivo pharmacodynamic studies can be examined. Heptabarbital was chosen as a model drug and several pharmacokinetic variables which may affect in-vivo concentration-pharmacological response relationships were examined. Adult female rats received an i.v. infusion of the drug at one of three different rates (0.225-1.50 mg min-1) until the animals lost their righting reflex (after 11 +/- 1 to 88 +/- 8 min of infusion). The serum concentration of the drug at onset of loss of righting reflex (LRR) increased slightly with increasing infusion rate. The drug concentrations in brain tissue and cerebrospinal fluid (CSF), (mean +/- s.d.: 67 +/- 5 mg kg-1 and 24 +/- 4 mg L-1, respectively, for the lowest infusion rate) were not affected by the infusion rate. The possible contribution of (inter)active metabolites to the pharmacological response of heptabarbital was determined by administration of different i.v. bolus doses (14.1-22.5 mg) resulting in widely differing sleeping-times (7 +/- 3 to 119 +/- 20 min). The concentrations of heptabarbital in serum, brain tissue and CSF at offset of LRR (mean +/- s.d.: 77 +/- 8 mg L-1, 76 +/- 7 mg kg-1 and 29 +/- 5 mg L-1, respectively, for the highest dose) were not affected by the administered dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gender Differences in the Pharmacodynamics of Barbiturates in Rats

There is considerable evidence of gender differences in the pharmacokinetics of numerous drugs, particularly in rodents, but very limited information concerning the effect of gender on pharmacodynamic characteristics (concentration-activity relationships). In this study, heptabarbital or phenobarbital was administered to male and female rats and the concentrations of these drugs in the brain, cerebrospinal fluid and serum at onset or offset of loss of righting reflex were determined. For heptabarbital, offset concentrations were determined in Lewis rats and onset concentrations in Wistar rats. Onset concentrations of phenobarbital were determined in Wistar rats. In all cases, the barbiturate concentrations in males were significantly lower than those in females at the pharmacologic endpoint. The biologic (serum) half-life of heptabarbital is much shorter in males (10 min) than in females (90 min) and this pharmacokinetic difference is reflected by the considerably longer duration of effect of the drug in females.     

Role of endothelin ETA receptors in sepsis-induced mortality,vascular leakage,and tissue injury in rats

The role of endothelin ETA receptors in sepsis-induced mortality and edema formation was evaluated with a selective antagonist ABT-627 [2-(4-methoxyphenyl)-4-(1,3-benzodioxol-5-yl)-1-(N,N-di(n-butyl)amino carbonylmethyl)-pyrrolidine-3-carboxylic acid]. Sprague-Dawley rats received saline (control group), Escherichia coli endotoxin (10 mg/kg, sepsis group) or infusion of ABT-627 prior and immediately after saline and endotoxin injection. Mortality, edema formation (wet/dry ratios), and multiple tissue injury (indicated by serum concentrations of creatinine, urea, bilirubin, creatine kinase, lactate dehydrogenase, and aspartate aminotransferase) were monitored within 5 h. Endotoxin injection elicited 64% mortality, significantly augmented edema formation in liver, heart, lung, and kidney, and raised serum levels of tissue injury markers. Pretreatment with ABT-627 completely reversed endotoxin-induced mortality, significantly attenuated wet/dry ratios of the heart, liver, and kidney, but not lungs, and reduced serum levels of creatine kinase, creatinine, aspartate aminotransferase, and lactate dehydrogenase, but not that of urea and bilirubin. These results suggest that endothelin ETA receptors play a significant role in promoting mortality, edema formation (except in the lungs), and tissue injury in animals with severe sepsis.     

Relationship between concentration and anticonvulsant effect of phenytoin against electroshock-induced seizures in rats: comparison of sampling sites for concentration determinations

The purpose of this investigation was to determine the optimum sampling site for phenytoin concentration measurements in the context of pharmacodynamic studies of the anticonvulsant effect of phenytoin. Determination of drug concentrations in the serum, serum water, brain, and cerebrospinal fluid (CSF) of rats as a function of time after iv injection of a 6-mg/kg dose revealed a significant disequilibrium between brain and serum water for 15 min and between CSF and serum water for 5 min after injection. The concentrations of phenytoin in serum water 1 min after injection of 3 mg/kg (0.371 +/- 0.054 microgram/mL) and 45 min after injection of 8 mg/kg (0.399 +/- 0.049 microgram/mL) were not significantly different, but drug concentrations in the CSF and brain were appreciably higher after the latter dose. There was no protection against electroshock-induced seizures 1 min after the 3-mg/kg dose, but there was complete protection 45 min after the 8-mg/kg dose. At 15 min after drug injection, phenytoin concentrations in CSF and serum water were essentially identical over a wide concentration range. Fifty female Lewis rats weighing approximately 225 g, that consistently exhibited maximal electroshock-induced seizures in three preliminary trials on separate days, received 1, 2, 4, 6, or 8 mg/kg of phenytoin by iv injection. Electroshock was applied 15 min later, the percentage of animals protected from seizure by each dose was determined, and drug concentrations in serum, serum water, brain, and CSF were measured by gas chromatography. The relationship between anticonvulsant activity and drug concentration could be described by a Hill-type equation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The antagonistic effect of chlorpromazine on cadmium toxicity

Adult male rats were injected sc with cadmium chloride (CdCl(2)) in a single dose of 7 mg/kg body wt. Twenty-four hours postinjection, exposure to CdCl(2) increased the hemoglobin absorbance of the testes from 0.36 +/- 0.01 to 2.46 +/- 0.02. Pretreatment of rats with chlorpromazine (CPZ) 3 mg/kg ip either for 1 or 2 days before exposure to CdCl(2) significantly (p < 0.05) reduced the testicular damage and the hemoglobin absorbance decreased to 1.03 +/- 0.02 and 0.92 +/- 0.04, respectively. After CdCl(2) injection there was a progressive increase in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. CdCl(2) injection induced hemorrhage and a diffuse area of coagulative necrosis in liver. Pretreatment with CPZ partially protected liver from the effect of CdCl(2). Two months postinjection, exposure to CdCl(2) significantly decreased the weights of testes, epididymis, and accessory sex organs. Furthermore, CdCl(2) induced a highly significant (p < 0.01) decrease in sperm cell concentration and the percentage of mobile cells. Moreover CdCl(2) induced degenerative changes in testes, epididymis, and seminal vesicles. Pretreatment with CPZ partially protected these organs from the toxic effects of CdCl(2). It could be concluded that chlorpromazine partially antagonized the toxic effects of cadmium on liver, testes, and other male reproductive organs of rats.     

Optimization of the dose and route of injection,and characterisation of the time course of carbon tetrachloride-induced hepatotoxicity in the rat

INTRODUCTION: The purpose of this study was to optimize carbon tetrachloride-induced hepatotoxicity in the rat with respect to dose, route of injection, and time course. METHODS: Male Wistar albino rats, 4 to 6 weeks old and weighing 130-180 g were used. Hepatotoxicity was evaluated by measuring the activity of serum enzymes (alkaline phosphatase [ALP], alanine aminotransferase [ALT], and aspartate aminotransferase [AST]) as well as serum total bilirubin level. RESULTS: Intraperitoneal injection of carbon tetrachloride (CCl(4)) increased the activity of ALP (from 64.9 to 137.3 U/l), ALT (from 106.6 to 693.1 U/l), and AST (from 113.8 to 693.9 U/l). Plasma bilirubin level increased (from 0.119 to 0.42 mg/dl). In contrast, subcutaneous injection of CCl(4) had no effect on these variables. The optimum intraperitoneal dose of CCl(4) was found to be 2 ml/kg body weight (dissolved in an equal volume of olive oil), and this increased the level of bilirubin and the activity of the three enzymes significantly, without causing death of the animals. Hepatotoxicity was observed within 2 h of intraperitoneal injection of CCl(4) and reached a peak after 24 h. Bilirubin level and serum enzyme activities declined gradually to normal levels by 3 days after CCl(4) injection. CONCLUSION: It is possible to reliably evoke reversible hepatotoxicity in rats by intraperitoneal injection of 2 ml/kg CCl(4).     

Prevention and reversal of tolerance to barbiturates by intraventricular injection of hemicholinium-3.

Intracerebroventricular (i.c.v.) injection of phenobarbital, 800 mug, or intraperitoneal (i.p.) injection of hexobarbital, 100 mg/kg, into rats resulted in a loss of righting reflex lasting 15.4 +/- 0.2 min and 20.7 +/- 0.7 min, respectively. A 40-60% reduction in this response was obtained following administration of phenobarbital either i.c.v. (800 mug 4 times daily) or i.p. (80 mg/kg/day) for 4 days. Although these treatments also increased hepatic mixed function oxidase activity, this enzyme induction was shown to be unrelated to the development of tolerance to loss of righting reflex. I.c.v. injection of hemicholinium-3 (HC-3) in doses which reduce brain acetylcholine levels (4-20 mug) profoundly affected tolerance to the central depressant effect of the barbiturates. Thus, depending upon the time of administration, HC-3 either retarded or prevented development of this tolerance. Moreover, if tolerance was allowed to progress normally, administration of HC-3 on day 4 or 5 returned the duration of the loss of righting reflex toward normal values. HC-3 did not influence either the duration of this response in non-tolerant rats or the induction of the hepatic mixed function oxidase activity. These results suggest that brain ACh plays an important role in the development and maintenance of tolerance to the central depressant effects of barbiturates.     

Effect of safranal on extracellular hippocampal levels of glutamate and aspartate during kainic Acid treatment in anesthetized rats

In this study, the effect of safranal, a constituent of CROCUS SATIVUS L., pretreatment on concomitant changes in the extracellular hippocampal levels of EAA (glutamate and aspartate) following systemic administration of KA was investigated in anesthetized rats. Safranal (72.75 mg/kg or 291 mg/kg, I. P.) was injected 40 min before KA (15 mg/kg, I. P.). A group of rats also received DZP (15 mg/kg, I. P.) 20 min prior to KA administration. The basal hippocampal concentrations of glutamate and aspartate were estimated to be 0.51 +/- 0.02 microM and 0.28 +/- 0.01 microM, respectively. Basal EAA levels were not affected by pretreatment with safranal. Following KA injection, there was a significant increase (p < 0.001) in the extracellular glutamate and aspartate levels (about 5-fold and 3-fold, respectively) at 80 min after injection. However, the kainite-evoked release of EAA was significantly reduced by DZP (p < 0.001) and safranal (291 mg/kg, I. P.; p < 0.001). The results of this study show that acute systemic injection of safranal reduces the extracellular concentrations of glutamate and aspartate in the rat hippocampus following KA administration.     

Kinetics of Drug Action in Disease States. XXXIX. Effect of Orally Administered Activated Charcoal on the Hypnotic Activity of Phenobarbital and the Neurotoxicity of Theophylline Administered Intravenously to Rats with Renal Failure

The central nervous system (CNS) sensitivity to the hypnotic (general anesthetic) action of pheno-barbital and to the neurotoxic (convulsive) action of theophylline is greater in rats with acute renal failure than in normal animals, consistent with clinical observations. In the case of phenobarbital, this increased sensitivity can be produced in normal rats by infusion of a solution of the lyophilized dialysate of serum from rats with renal failure. It was hypothesized that the relevant constituent(s) of this dialysate may circulate between the blood and the intestinal lumen and that it (they) can be adsorbed by orally administered activated charcoal and thereby removed from the body. If so, treatment of renal failure rats with activated charcoal should partly reverse the increased CNS sensitivity to phenobarbital and to other drugs similarly affected. Accordingly, rats with renal failure produced by bilateral ligation of ureters were given an aqueous suspension of activated charcoal, about 1 g per kg body weight, orally every 8 hr for six doses. Uremic controls received equal volumes of water. About 2 hr after the last dose, the animals were infused i.v. with phenobarbital to onset of loss of righting reflex or with theophylline to onset of maximal seizures. In the phenobarbital study, charcoal treatment partly reversed the hypothermia associated with renal failure and caused a reduction of creatinine and total bilirubin concentrations in serum. The cerebrospinal fluid (CSF) concentration of phenobarbital at onset of loss of the righting reflex was significantly higher in charcoal treated rats than in their controls. In the theophylline experiment, charcoal treatment had no significant effect on the measured biochemical variables but caused a large increase in the dose and concentrations of theophylline required to produce maximal seizures. In both experiments, administration of activated charcoal caused a reversal of the hyperalgesia associated with renal failure, as determined before drug administration by tail flick latency. These results are consistent with the hypothesis that oral administration of activated charcoal can cause a reduction in the concentration of the circulating endogenous substance(s) that alters the pharmacodynamics of certain drugs in renal failure.     

Pharmacodynamics of tolerance development to the anesthetic and anticonvulsant effects of phenobarbital in rats

In this study, the potential development of tolerance towards the anesthetic and anticonvulsant effects of phenobarbital after chronic administration to rats was investigated, differentiating between dispositional and functional tolerance. Chronic exposure to phenobarbital by daily ip injections of 20 or 100 mg/kg for 14 days caused a 30% increase in clearance within 1 week. No changes occurred in the total amounts of phenobarbital and para-hydroxyphenobarbital excreted into urine and feces. Pharmacodynamic effects were quantitated after 2 weeks of treatment. The anesthetic effect was measured by slow iv infusion of phenobarbital until onset of loss of righting reflex (LRR), followed by measurement of drug concentrations in serum (both total and free), brain, and cerebrospinal fluid (CSF). With a phenobarbital dose of 100 mg/kg daily, CSF concentrations at the onset of LRR significantly increased from 136 +/- 12 to 176 +/- 21 mg/L (p less than 0.001), indicating that functional tolerance developed for the anesthetic effect. Protection of phenobarbital against convulsions induced by pentylenetetrazol (PTZ), as measured by the elevation of the PTZ plasma threshold concentration necessary to elicit seizures at the EC50 of phenobarbital, was not altered. The discrepancy observed in the development of functional adaptation of the CNS demonstrates that different mechanisms of action are reflected in the different measures of the anesthetic and anticonvulsant effects of phenobarbital that were utilized.     

Toxicity of polycyclic aromatic hydrocarbons. I. Effect of phenanthrene, pyrene, and their ozonized products on blood chemistry in rats

Male Sprague-Dawley rats were treated with a single ip injection of physiological saline (3.0 ml/kg), dimethyl sulfoxide (DMSO, 3.0 ml/kg), phenanthrene (150 mg/kg), ozonized products of phenanthrene (150 mg/kg), pyrene (150 mg/kg), or ozonized products of pyrene (150 mg/kg). Phenanthrene, pyrene, and their ozonized products were dissolved in DMSO (50 mg/ml). Serum aspartate aminotransferase (AST) activity was increased significantly 24 hr after ip administration of DMSO when compared with physiological saline. Phenanthrene produced a significant elevation of serum AST and gamma-glutamyl transpeptidase (GGTP) levels related to physiological saline and DMSO-injected rats 24 hr after injection. However, GGTP levels for groups treated with DMSO or phenanthrene were not significantly increased when compared with saline groups 72 hr after injection. Ozonized products of phenanthrene produced a significant elevation of serum AST, alanine aminotransferase (ALT), GGTP, and bilirubin levels when compared with groups treated with physiological saline, DMSO, and phenanthrene 24 or 72 hr after injections. The ozonized products of phenanthrene also produced significant elevation of serum creatinine levels compared with physiological saline, DMSO, and phenanthrene groups at 24 hr after treatment and of blood urea nitrogen (BUN) levels at 24 and 72 hr. Although pyrene caused a small but significant increase in the serum AST and bilirubin levels 24 hr after treatment, no significant change in the serum AST, ALT, GGTP, BUN, and creatine levels were observed with the ozonized products of pyrene at 24 or 72 hr. This study demonstrates significant alterations in serum chemistry induced by reaction products of ozone with phenanthrene. No such effect was observed when the products of pyrene ozonation were administered. Although the ozonation products of pyrene were not toxic under the conditions of this study, phenanthrene products were more hepatotoxic than was phenanthrene itself. Nephrotoxicity was also an apparent effect of ozonized phenanthrene. Since ozone-polycyclic aromatic hydrocarbon (PAH) reactions may occur in the atmosphere, these reactions might produce compounds that are more toxic than either ozone or the PAH alone.     

15d-prostaglandin J2 reduces multiple organ failure caused by wall-fragment of Gram-positive and Gram-negative bacteria

Septic shock is still the major cause of death in surgical intensive care units. Both gram-positive (G+) and gram-negative (G-) bacteria have been isolated in the blood of a large portion of septic patients, and these polymicrobial infections often have a higher mortality than infections due to a single organism. Cell wall fragments from G+ and G- bacteria synergise to cause shock and multiple organ dysfunction in vivo (G+/G- shock). Male Wistar rats were anaesthetised and received a coadministration of wall fragments from G+ and G- bacteria, Staphilococcus aureus (S. aureus) peptidoglycan [0.3 mg/kg, intravenously (i.v.)] and Escherichia coli (E. coli) lipopolysaccharide (1 mg/kg, i.v.) or vehicle (saline, 1 ml/kg, i.v.). G+/G- shock for 6 h resulted in an increase in serum levels of creatinine (indicator of renal dysfunction), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (gamma-GT), bilirubin (markers for hepatic injury and dysfunction) and creatine kinase (CK, an indicator of neuromuscular, skeletal muscle or cardiac injury). Pretreatment of rats with the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist 15d-prostaglandin J2 (0.3 mg/kg, i.v., 30 min prior to G+/G-) reduced the multiple organ injury/dysfunction caused by coadministration of peptidoglycan+lipopolysaccharide. The selective PPAR-gamma antagonist GW9662 (2-Chloro-5-nitrobenzanilide) (1 mg/kg, i.v., given 45 min prior to G+/G-) abolished the protective effects of 15d-prostaglandin J2. 15d- prostaglandin J2 did not affect the biphasic fall in blood pressure or the increase in heart rate caused by administration of peptidoglycan+lipopolysaccharide. The mechanism(s) of the protective effect of this cyclopentenone prostaglandin are-at least in part-PPAR-gamma dependent, as the protection afforded by 15d-prostaglandin J2 was reduced by the PPAR-gamma antagonist GW9662. We propose that 15d-prostaglandin J2 or other ligands for PPAR-gamma may be useful in the therapy of the organ injury associated with septic shock.     

Pharmacodynamics of the hypnotic effect of salicylamide in rats

Salicylamide (SAM) can produce sedation and sleep in humans and animals. To explore the potential utility of the drug as a research tool for assessing disease effects on the response of the central nervous system to depressant drugs, and to obtain a better understanding of the clinically evident sedative action of SAM, studies were performed to characterize the relationship between the concentrations and hypnotic effect of this drug in rats. Female Lewis rats weighing 170-200 g received SAM by intravenous infusion at a rate of 0.49, 1.22, or 2.47 mg/min until the onset of loss of the righting reflex. This well-defined pharmacological endpoint occurred from 16.7 +/- 2.3 min (fastest infusion rate) to 110 +/- 27 min (slowest infusion rate) after the start of the infusion. SAM concentrations at that time in serum, serum water, brain, and cerebrospinal fluid (CSF) were similar in animals that had received the 1.22- or 2.47-mg/min infusion and lower in animals that were infused at a rate of 0.49 mg/min. The slowest infusion rate group also exhibited increased serum protein binding of the drug. The SAM concentration ratio, CSF-serum water, was essentially unity in all three groups, indicative of rapid equilibration of the drug across the blood-CSF barrier. Gentisamide, the hydroxylated metabolite of SAM, was found in serum, CSF, and brain, but in low concentrations at which this metabolite alone had no hypnotic effect.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study of unfractionated and low molecular weight heparins in a model of cholestatic liver injury in the rat.

Forty-eight rats with biliary obstruction induced by double ligation and section of the common bile duct were randomly and blindly assigned to receive subcutaneous injection of either conventional heparin sodium (1000IU kg(-1)), three already marketed low molecular weight heparin (LMWH) preparations: nadroparin (1000 anti-Xa IU kg(-1)), tinzaparin (1000 anti-Xa IU kg(-1)), enoxaparin (180 anti-Xa IU kg(-1)) or saline. Drugs were administered once a day, starting 7 days after surgery and continued for 3 weeks. At the end of the treatment period, rats were killed and analyzed for blood biochemistry and liver pathology. Liver fibrosis was assessed by image analysis. Data indicated that treatment with nadroparin decreased plasma total bilirubin, serum alkaline phosphatase (ALP) and gamma glutamyltransferase (GGT) levels by 80.3, 70.7 and 42%, compared with bile duct ligated (BDL) control values. The reduction in plasma total protein observed in BDL controls was prevented by nadroparin. Enoxaparin-treated rats showed significant reduction in plasma total bilirubin and alanine aminotransferase levels by 32.5 and 38.4% versus BDL controls. Liver necrosis evaluated histologically was significantly reduced in the nadroparin- and enoxaparin-treated rats. Morphometric analysis showed significant reduction in fibrosis on nadroparin and enoxaparin treatment: area of fibrosis: 1.66 +/- 0.17% and 14.03 +/- 1.1% versus 18.94 +/- 2.4% (P<0.05); nadroparin and enoxaparin versus BDL control. By contrast, neither conventional heparin nor tinzaparin prevented the bile duct ligation-induced liver damage as indicated by increased plasma aminotransferases, ALP and GGT concentrations and the histological evidence of necrosis. Total serum bilirubin was increased by 27.5% in rats treated with conventional heparin, while ALP and GGT levels were 38.6 and 31.4% higher after tinzaparin treatment versus BDL controls. Significant increase in the area of fibrosis was observed after tinzaparin treatment compared to BDL control group. Results suggest a beneficial effect for nadroparin and enoxaparin in the therapy of patients with obstructive jaundice or cholestatic liver disorders. The present data from bile duct ligated rats suggest an antifibrotic effect for nadroparin and enoxaparin.     

Quantitative and qualitative changes of serum proteolytic activity in rats with liver damage induced by galactosamine

Serum proteolytic activity was determined in galactosamine-treated rats and in controls. Injection of the hepatotoxin at a dose of 400 mg/kg resulted in a 3.4-fold elevation in the serum proteolytic activity, while AST (aspartate aminotransferase), ALT (alanine aminotransferase) and bilirubin were increased by factors of 3.9, 8.8 and 4.5, respectively. Studies with proteinase inhibitors revealed that the serum proteolytic activity was partially metal-dependent as well as puromycin and antipain sensitive. Differences in susceptibility to a combination of N-ethylmaleimide and antipain indicated presence of different proteolytic systems in the sera of liver damaged and control rats. Separation of serum proteinases by gel filtration showed that the galactosamine-intoxicated rat serum contained activity which did not appear in the control serum. This activity was partially metal dependent, antipain and N-ethylmaleimide sensitive, and was more susceptible to dithiothreitol than the control activity. These findings demonstrate that hepatocellular damage induced by galactosamine caused not only an increase in serum proteinases, but was also associated with the appearance of enzymes not normally released by the liver of untreated animals.Abbreviations AP alkaline phosphatase - TBil total bilirubin - AST aspartate aminotransferase - ALT alanine aminotransferase - GGT gamma-glutamyltranspeptidase - BiAc bile acids - PrAm primary amines - ProAc proteolytic activity     

Prevention of acute adriamycin cardiotoxicity by dantrolene in rats

Possible preventive effect of dantrolene against the peroxidative damage in rat heart which was induced by the administration of an acute dose of adriamycin (ADR, 20 mg/kg, i.p.) has been examined. Forty-eight hours after ADR administration, biochemical changes including the activities of serum creatine kinase isoenzyme (CK-MB), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) and the levels of malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in heart tissue were measured. Pretreatment of rats with dantrolene, given i.p. 30 min prior to ADR injection, substantially reduced the peroxidative damage in the myocardium, and markedly lowered the serum CK-MB, LDH and AST. The protective effects obtained by dantrolene administration, however, were not complete and did not reach those of the control group. Dantrolene, at 5 mg/kg, was useful to obtain significant protective effects, while the protector effect of higher dantrolene dosing level (10 mg/kg) was weak or absent. These results suggest that, at least in part, due to antioxidative properties, dantrolene may provide a significant protective effect against acute ADR-induced cardiotoxicity.     

Studies on the hepatotoxicity induced by bis (tributyltin) oxide

The toxic effects of bis (tributyltin) oxide (TBTO) on the rat liver were studied with an electron microscope and the accumulation sites of tin were determined with an X-ray microanalyzer. The activities of serum enzymes and the concentration of serum bilirubin were also analyzed. Male Wistar rats received an intramuscular injection of 0.5 ml/kg of TBTO. Marked swelling of the mitochondria appeared in the hepatocytes 4 h after injection of TBTO. Cytoplasmic vacuoles, which contained degenerated mitochondria, gradually increased in number in these hepatocytes. This in turn may have caused a decrease in the volume of hepatic cell cords and an enlargement of sinusoids in the entire hepatic lobule. However, fine structures of intrahepatic bile ducts were not altered. By X-ray microanalysis, tin peaks were preferentially obtained from swollen mitochondria of the hepatocytes. By polarographic analysis of the respiratory responses of mitochondria, it was demonstrated that rates of state 4 respiration and respiratory control ratio were significantly disturbed in TBTO-treated rats in comparison with those of controls. The activities of AST (aspartate aminotransferase) and ALT (alanine aminotransferase) were significantly increased after TBTO treatment, but those of ALP (alkaline phosphatase), LAP (leucine aminopeptidase) and total bilirubin were not changed. These results indicated that parenterally administered TBTO accumulated in the liver cell mitochondria and disturbed oxidative phosphorylation. Mitochondrial dysfunction might induce severe damage of the hepatocytes. Four days after injection of TBTO, hepatic structures and chemical indices were almost restored by the regeneration of hepatocytes.     

Effect of propolis extract on D-galactosamine-induced hepatic injury in rats

The preventive effect of propolis extract on D-galactosamine-induced hepatic injury was examined in rats. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were significantly increased at 24 h after intraperitoneal injection of D-galactosamine (400 mg/kg) in the animals. Propolis extract was administered orally three times in doses of 3 or 30 mg/kg at 18 h and 1 h before and 8 h after D-galactosamine injection. The extract itself and the vehicle alone (dextran) caused no significant changes in serum AST or ALT activities. Treatment with the extract dose-dependently prevented the increases in serum AST and ALT activities induced by D-galactosamine, and significant inhibition was observed at a dose of 30 mg/kg. These results suggested that propolis extract may have an ameliorating effect on hepatic dysfunction.