Prevention by silymarin of membrane alterations in acute CCl4 liver damage

The effect of silymarin on liver lipid peroxidation and membrane lipid alterations induced by an acute dose of CCl4 was studied. Four groups of animals were treated with CCl4, CCl4 + silymarin, silymarin and its vehicles. CCl4 was given orally (0.4 g 100 g-1 body wt.) and silymarin was administered i.p. All animals were sacrificed 24 h after the treatments. Liver lipid peroxidation was measured and plasma membranes were isolated. Alkaline phosphatase (AP) and gamma-glutamyl transpeptidase (GGTP) were measured in plasma membranes. Membrane lipids were extracted and then analysed by thin-layer chromatography by measuring the phosphorus of the phospholipids in each spot. Liver lipid peroxidation was increased about three times in the group receiving CCl4 only. Silymarin cotreatment prevented this increase. Phosphatidylethanolamine (PEA) decreased, while phosphatidylinositol (PI) increased in the plasma membranes isolated from the CCl4-treated group. Animals that received CCl4 + silymarin showed no decrease in PEA content. A partial prevention of the decrease in phosphatidylinositol content was also observed in plasma membranes of animals treated with silymarin in addition to CCl4. CCl4 decreased gamma-glutamyl transpeptidase (GGTP) and alkaline phosphatase (AP) membrane activities. Silymarin cotreatment prevented the AP (completely) and the GGTP (partially) falls caused by CCl4. Silymarin by itself increased AP membrane activity. A significant relationship between the membrane content of phosphatidylethanolamine (PEA) and the AP activity was observed in plasma membranes of treated animals and in normal liver membranes enriched with PEA. These results indicate that silymarin can protect against the alterations induced by CCl4 on the liver plasma membrane through its antioxidant properties by modifying the plasma membrane phospholipid content.     

The role of membrane composition in ATPase activities of cirrhotic rat liver: effect of silymarin

The activities of Ca2(+)- and Na+, K(+)-ATPases were studied in liver plasma membranes from CCl4-cirrhotic rats and from livers of rats treated with silymarin in addition to CCl4. CCl4 chronic treatment produced significant decreases in Na+, K(+)- and Ca2(+)-ATPase activities; however, the animals treated with silymarin along with CCl4 showed no differences in ATPase activities as compared to controls. The lipid analysis performed in plasma membranes revealed increases in the cholesterol/phospholipid (CH/PL) and sphingomyelin/phosphatidylcholine (SM/PC) ratios in the cirrhotic group. Again, the membranes isolated from rats receiving CCl4 + silymarin showed normal CH/PL and SM/PC values. Considering that CH/PL and SM/PC ratios are related to membrane microviscosity, this study suggests that a lower fluidity of the membrane may be responsible for the observed decreases in ATPase activities in the cirrhotic group. Additionally, the role of silymarin to improve liver function in CCl4-cirrhosis can be attributed partially to its action at membrane level by preventing the increases in CH/PL and SM/PC ratios.     

Evaluation of liver weight changes following a single oral administration of carbon tetrachloride in rats

To evaluate liver weight changes resulting from the primary toxic effect of carbon tetrachloride (CCl4), male and female rats were assigned to a control group, CCl4-treated groups administered a single po dose of 100 microliters (males only) or 200 microliters CCl4/100 g body wt, or a "hold" group in which the body weight change of the CCl4-treated group was duplicated by imposing restrictions of movement and feeding. Five rats from each group were killed at 1, 2, 3, 4, and 6 days after treatment, and body weight, food intake, and liver weight were tabulated. It was found that presentation of liver weight data in absolute terms may lead to erroneous conclusions, since the absolute liver weights of the CCl4-treated males showed changes similar to those of the control group, as if there had been no effect of CCl4 on liver weight. Furthermore, the results for the hold group (males and females) showed that there was not a linear relationship between liver weight and body weight during the period of rapid decrease in body weight, suggesting that comparisons made in terms of relative organ weights do not necessarily take proper account of differences in body weight. From the profile of the percentage absolute liver weight increases (delta W) of the CCl4-treated group from the levels in the hold group, it was concluded that CCl4 does induce an increase in liver weight following a single dose, and the effect on liver weight reached a maximum at 24 to 48 hr. These results demonstrate the need for great care in evaluating the direct effect of chemicals on organ weight when rapid changes in body weight are also occurring.     

Evidence for increased membrane permeability of plasmalemmal vesicles from livers of phenobarbital-induced CCl4-intoxicated rats

We have observed a marked increase in Ca2+ permeability of plasma membranes isolated from rats treated in vivo with CCl4 (2 ml/kg), after phenobarbital induction and overnight fast. Regulation of intracellular free Ca2+ is vital to cell viability and function, and the increased plasma membrane permeability, if representative of a change occurring in vivo, may be a critical biochemical determinant of CCl4-induced hepatic necrosis. Permeability to small cations of liver plasma membrane vesicles of control and CCl4-dosed rats was tested by two independent methods: 1) Ca2+ efflux after passive loading in 1 mM Ca2+, and 2) 86Rb+ uptake driven by valinomycin-induced K+ diffusion potential after 100 mM KCl-equilibrated vesicles were stripped of external K+ by cation exchange. Both indicated markedly increased permeability in plasma membranes after CCl4 in vivo. First order rate constants of biphasic Ca2+ efflux were 0.272 and 0.0516 min-1 for controls and 1.78 and 0.171 min-1 for vesicles from CCl4-treated animals. 86Rb+ uptake by CCl4 vesicles was 47% of control. Total calcium contents of plasma membranes (prepared in the absence of EGTA) by atomic absorption were 17.4 +/- 2.0 (control) and 10.9 +/- 1.2 (CCl4) nmol/mg of protein (means +/- SE, p less than 0.025). In correlation with altered biochemical function, we found 4-fold increases in the content of 11-, 12-, and 15-hydroxyeicosatetraenoic acids in plasma membranes of CCl4-treated rats. Although these specific oxidized fatty acids are unlikely to be ionophores, the ionophoretic properties of certain other oxygenated polyunsaturated fatty acids suggest a mechanism whereby accumulation of lipid oxidation products may be responsible for the altered membrane permeability we have observed after CCl4, and perhaps ultimately for cell death in CCl4-induced hepatic necrosis.     

Carbon tetrachloride-induced changes in the activity of phase II drug-metabolizing enzyme in the liver of male rats: role of antioxidants

Glutathione S-transferases and glutathione play an important role in the detoxification of most toxic agents. In the present study, the protective effects of some antioxidants (L-ascorbic acid (AA), vitamin E (VE) or garlic) on carbon tetrachloride-induced changes in the activity of alanine amino transferase (ALT), aspartate amino transferase (AST), glutathione S-transferase (GST), and the level of glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) were studied. The activities of ALT, and AST were assayed in plasma, whereas the activity of GST and the levels of GSH and TBARS were determined in the livers of rats. The current study included two experiments. In the first experiment, animals received single oral dose of CCl4 (400 mg/kg body weight) after administration of AA (100 mg/kg b.w.), VE (100 mg/kg b.w.) or garlic (800 mg/kg b.w.) as single oral doses. In the second experiment, rats received repeated oral doses of antioxidants for 12 consecutive days followed by a single oral dose of CCl4 on the 13th day and killed after that by 24 h. Treatment of male rats with CCl4 significantly increased the activity of ALT and AST in plasma, and the levels of both GSH and TBARS in the liver. On the other hand, CCl4 inhibited the activity of GST after single dose treatment. Single-dose treatments of rats with AA, VE or garlic prior to the administration of CCl4 could not restore the alterations in the activity of ALT and AST caused by CCl4 to the normal control level. However, repeated dose treatments with these agents restored such alterations to the normal level. We observed that VE is more effective than AA and garlic in restoring the inhibition of GST activity caused by CCl4 to the normal level after single dose treatments. On the other hand, AA and VE are more effective than garlic in restoring the induced TBARS level caused by CCl4 to the normal control level after repeated dose treatments. It has been observed that the tested antioxidants were able to antagonize the toxic effects of CCl4, and such counteracting effects were more pronounced when they were administered as repeated doses prior to administration of CCl4.     

Lipid peroxidation and irreversible cell damage: synergism between carbon tetrachloride and 1,2-dibromoethane in isolated rat hepatocytes

The combination of 1,2-dibromoethane (DBE) with carbon tetrachloride (CCl4) in the isolated rat hepatocyte model produces a significant potentiation of both lipid peroxidation and plasma membrane damage induced by the latter compound. The increase in malondialdehyde production precedes the hepatocyte damage, evaluated in terms both of lactate dehydrogenase leakage and trypan blue exclusion. When hepatocytes are isolated from vitamin E pretreated rats, both the prooxidant and the cytotoxic effects of CCl4 are prevented. Also the synergism between CCl4 and DBE on lipid peroxidation disappears completely while that on cell damage is strongly reduced. The increased lipid peroxidation appears to be one of the mechanisms of the observed synergism between CCl4 and DBE on hepatocyte damage. Regarding the antioxidant status of the hepatocyte challenged with CCl4 and DBE, an early and significant consumption of vitamin E is observed only in the presence of the mixture of these xenobiotics. Total nonprotein thiol content is not significantly modified by CCl4 poisoning while DBE, alone and in association with CCl4, markedly decreases it. Vitamin E supplementation does not prevent but moderately delays total nonprotein thiol depletion due to DBE or to the mixture. Finally, glutathione transferase activity is significantly reduced by CCl4 treatment and not by DBE, and vitamin E supplementation totally prevents such inhibition. The increased prooxidant effect of CCl4 plus DBE compared to CCl4 alone seems related to the shift in DBE metabolism consequent to the CCl4-dependent inactivation of glutathione transferase.     

Chlorzoxazone: a probe drug the metabolism of which can be used to monitor one-point blood sampling in the carbon tetrachloride-intoxicated rat.

In this study, we have carried out an investigation to determine if chlorzoxazone (CZX) is a suitable probe drug for predicting hepatic injury in carbon tetrachloride (CCl4)-intoxicated rats. The animals received oral doses of CCl4 (0.25, 0.5 and 1 ml/kg) 24 h prior to intraperitoneal administration of CZX. The total CYP and CYP2E1 content, as well as the aniline and CZX hydroxylase activity (Vmax and CLint), was reduced depending on the dose of CCl4 administered. At the highest concentration (128 mM) of diethyldithiocarbamate, a specific inhibitor of CYP2E1, the production of 6-hydroxychlorzoxazone (HCZX) in microsomes from CCl4-treated rats was reduced by about 85%. The IC50 value in microsomes from CCl4-treated rats was between 3 and 5 microM. The production of HCZX and the activity of aniline hydroxylase in CCl4-treated rats correlated with the amount of rat CYP2E1 protein (r=0.881, P<0.001 and r=0.822, P<0.001, respectively). The elimination of CZX by CCl4-treated rats was reduced and the HCXZ production in the CCl4-treated group was less than that in the olive oil-treated control group. The correlations between the intrinsic clearance [CLint: Vmax/Km) in vitro and the total body clearance (CLtot) of CZX hydroxylation and the elimination half-life (t1/2) of CZX in vivo in CCl4-treated rats were high (r=0.839, P<0.001 and r= -0.828, P<0.001, respectively). In addition, the metabolic plasma HCZX/CZX ratio did not require multiple blood sampling and, 2 h after CZX administration in vivo, there was also a high correlation with the CLint (Vmax/Km) in vitro (r= -0.909, P<0.01). In conclusion, these results from this study demonstrate that CZX is a good probe for monitoring the inhibition of metabolism in rats due to CCl4 treatment.     

Vitamin E and selenium in gentamicin nephrotoxicity

1. The sequence of renal cellular membrane damage induced by gentamicin was studied in the rat by using the release of alkaline phosphatase, acid phosphatase, muramidase and protein from renal cells as indices of renal damage. 2. The protective effect of a combination of vitamin E and selenium against renal damage was also investigated. 3. Gentamicin (60 mg kg-1 body weight) was nephrotoxic within 12 h of the first dose. 4. The plasma membrane of the renal tubules is damaged before the lysosomal membrane is affected. 5. A combination of vitamin E (1 mg g-1 body weight) and selenium (4 x 10(-3) mg g-1 body weight) attenuates the renal damage induced by gentamicin. Results suggest synergism between vitamin E and selenium in attenuating the renal damage. The possible mechanism of attenuation is discussed. 6. Vitamin E and selenium may have anti-diuretic potential.     

Effect of cyclosporin A on the membrane-associated events in human leukocytes with special reference to the similarity with dexamethasone

The effect of an immunosuppressive drug, cyclosporin A, and dexamethasone was assessed on the enzymatic reactions of membrane phospholipid in normal human lymphocytes and neutrophils. Incubation for 20 min with cyclosporin A markedly suppressed, in a dose dependent manner, phospholipase A2 activity and the release of prostaglandin E2 in lymphocytes, and slightly those in neutrophils, while no inhibition of phosphatidylethanolamine (PE)-N methyltransferase activity was observed. Choline phosphotransferase (CPT) activity was not inhibited by the drug, either. These inhibitory effects on enzyme activities of membrane phospholipid are similar to those of dexamethasone, although different incubation time of the drug was required to induce inhibitory effects. These findings suggest that cyclosporin A acts upon early membrane events in the activation of cells involved in inflammatory reactions; they further suggest that suppression of immune response by cyclosporin A is at least partly due to inhibition of phospholipase A2 in the plasma membrane of inflammatory cells. This inhibition reduces the production of cell membrane lyso-phosphatidylcholine (PC) and arachidonic acid from PC, which is produced by transmethylation of PE and cytidine diphosphate (CDP) choline pathway of which the last reaction to PC is mediated by CPT.     

Serum aminotransferase activity as a predictor of clearance of drugs metabolized by CYP isoforms in rats with acute hepatic failure induced by carbon tetrachloride

The values of serum aminotransferase activity (AST) in untreated rats and rats with acute hepatic failure at 24h after an oral administration of CCl(4) (0.5 ml/kg) were 85+/-9 IU/l and 4260+/-620 IU/l (mean+/-S.D., n=6), respectively. The values of total clearance (CL(tot)) after intravenous administration of caffeine, tolbutamide, chlorzoxazone or lidocaine (as probe drugs for various CYP isoforms) to CCl(4)-treated rats were decreased to about 1/8, 1/3, 1/3 or 1/2 compared with those in untreated rats. Good correlations were observed between mRNA expression and enzyme activity of CYP2C11, CYP2E1, CYP3A2 and CYP1A2 in livers of rats given various doses of CCl(4). There was also a good negative correlation between serum AST activity and hepatic enzyme activity of each CYP. The serum AST activities corresponding to a 50% decrease of CYP2C 11, CYP2E1, CYP3A2 and CYP1A2 activities were about 710, 780, 1030 and 1300 IU/l, respectively. In conclusion, when the serum AST value in CCl(4)-treated rats reached about 4000 IU/l, the hepatic CYP activities were one-tenth or less of the control, although the degree of decrease of the CL(tot) values varied markedly. Nevertheless, the AST value appears to be a promising candidate for an indicator to predict appropriate dose modification of drugs for patients with acute hepatic failure.     

Evaluation of liver weight changes following repeated administration of carbon tetrachloride in rats and body-liver weight relationship

The proper method of evaluating liver weight changes resulting from the primary toxic effect of a chemical was studied. We used a pair-feeding method with carbon tetrachloride (CCl4), a chemical known to cause an increase in liver weight. Male rats were assigned to an untreated control group, CCl4-treated groups (daily dose of 10 microliter or 50 microliter of CCl4 in olive oil/100 g body wt), olive oil-treated plus feed-restricted groups, and feed-restricted groups. In the 2 types of feed-restricted groups the body weight changes of the CCl4-treated groups were duplicated by imposing restrictions on feeding. Absolute and relative liver weights were compared among the 4 types of groups after treatment for 14 or 25 days. Either absolute or relative liver weight of the treated group when compared to that of the feed-restricted group was the most reliable and sensitive toxicity indicator. In comparing the treated group with the untreated control group, relative liver weight was a more sensitive toxicity indicator than absolute liver weight. However, when liver weight data for about 200 normal male rats were plotted against body weight, and the 95% confidence limits of the regression line (y = ax) were estimated, most of the data for the feed-restricted rats were outside the lower confidence limit. This means that a comparison of the relative liver weights of the treated rats and untreated control rats is not strictly valid, because the body weight-liver weight relationships are not the same in the 2 groups.     

Carbon tetrachloride-induced nephrotoxicity and DNA damage in rats: Protective role of vanillin

In this study, the protective effects of vanillin were evaluated against carbon tetrachloride (CCl(4))-induced kidney damages in Wistar albino rats. CCl(4) (1 ml/kg, intraperitoneally [i.p.]) caused a significant induction of renal disorder, oxidative damage and DNA fragmentation as evidenced by increased plasma creatinine, urea and uric acid levels, increased lipid peroxidation (malondialdehyde [MDA]) and protein carbonyl. Furthermore, glutathione levels, catalase, superoxide dismutase, glutathione transferase and glutathione peroxidase activities were significantly decreased. A smear without ladder formation on agarose gel was also shown, indicating random DNA degradation. Pretreatment of rats with vanillin (150 mg/kg/day, i.p.), for 3 consecutive days before CCl(4) injection, protected kidney against the increase of MDA and degradation of membrane proteins compared to CCl(4)-treated rats and exhibited marked prevention against CCl(4)-induced nephropathology, oxidative stress and DNA damage. Kidney histological sections showed glomerular hypertrophy and tubular dilatation in CCl(4)-treated rats, however, in vanillin pretreated rats, these histopathological changes were less important and present a similar structure to that of control rats. These data indicated the protective role of vanillin against CCl(4)-induced nephrotoxicity and suggested its significant contribution of these beneficial effects.     

Aspirin disposition in rats acutely intoxicated with CCl4

The profile of urinary salicylate metabolites was determined after an oral administration of acetylsalicylic acid (ASA) to: 1, control rats; 2, rats treated with CCl4 and 3, rats intoxicated with CCl4 and also pretreated with colchicine for 7 days. The following enzymatic activities were determined: liver and plasma ASA-esterase, liver UDP-glucuronyltransferase and liver aniline hydroxylase. The time course of plasma concentration of salicylates in similar groups were followed after the intraperitoneal administration of acetylsalicylic acid (ASA), salicylic acid (SA) or gentisic acid (GA). The animals acutely intoxicated with CCl4 showed a reduction in urinary excretion of glucuronates and an increased urinary excretion of gentisic and salicylic acids. The activities of plasma and liver ASA-esterases were significantly increased in CCl4-treated rats while the aniline hydroxylase was reduced and the UDP-glucuronyltransferase remained unchanged. The plasma half lives of salicylates were reduced in CCl4-treated rats regardless of the administered parent compound. Colchicine pre-treatment completely prevented the alterations produced by acute intoxication with CCl4. The heterogeneity of liver metabolic dysfunctions present in acute liver damage was evidenced. It is emphasized that the pharmacokinetic alterations produced by acute liver injury can be the result of complex factors that may involve changes in circulation, hepatic binding protein and other routes of elimination.     

Development of an experimental model of liver cirrhosis in rabbits

1. The aim of the present study was to develop an experimental model of liver cirrhosis in rabbits using CCl4 and phenobarbital. 2. Liver cirrhosis was induced in male New Zealand white rabbits (n = 10) by intragastric administration of CCl4 once weekly starting 14 days after the addition of phenobarbital to the drinking water (50 mg/day). Controls received phenobarbital only (n = 7). Alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), albumin and bilirubin levels were determined throughout CCl4 treatment. The initial dose of CCl4 was 20 microg and subsequent doses were calculated to maintain AST and ALT levels between 400 and 800 IU/L for the duration of treatment (16 weeks). Indocyanine green (ICG) clearance was performed before and at the end of CCl4 treatment. Animals were killed at 16 weeks and three fragments of each liver lobe were processed for histological examination. A semiquantitative score was used to evaluate the development of fibrosis. 3. Cirrhosis developed in 80% of rabbits treated with CCl4. These animals did not gain weight compared with controls (P < 0.05). A significant reduction of ICG clearance was observed in CCl4-treated rabbits compared with controls (P < 0.05). The AST, ALT, bilirubin and gamma-GGT levels were elevated in CCl4-treated rabbits. 4. In conclusion, this model is successful in producing liver cirrhosis and may be useful in studies investigating metabolic, immunological or biochemical changes during the evolution of chronic liver disease.     

Comparative effects of curcumin and an analogue of curcumin in carbon tetrachloride-induced hepatotoxicity in rats

We have evaluated the comparative effect of curcumin (diferuloyl methane) and its analogue [bis-1,7-(2-hydroxyphenyl)-hepta-1,6-diene-3,5-dione] (BDMC-A) on carbon tetrachloride-induced hepatotoxicity in rats. Administration of carbon tetrachloride (3 ml/kg/week) for three months significantly (P<0.05) increased the levels of marker enzymes such as aspartate transaminase (AST), alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT). The levels of plasma thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides were also significantly (P<0.05) increased. We have observed a significant (P<0.05) decrease in the levels of plasma reduced glutathione (GSH), vitamin C and vitamin E. There was a significant (P<0.05) increase in the levels of TBARS and hydroperoxides in liver and kidney and a significant (P<0.05) decrease in the activities of enzymic antioxidants- superoxide dismutase (SOD), catalase and GSH peroxidase along with GSH in CCl(4)-treated rats. Oral administration of curcumin and BDMC-A to CCl(4)-induced rats for a period of three months significantly (P<0.05) decreased the levels of marker enzymes, plasma TBARS and hydroperoxides and increased the levels of plasma and tissue antioxidants. Histopathological studies of liver also showed protective effect of curcumin and BDMC-A. We have observed thickening of blood vessels and microvesicular fatty changes around the portal triad in CCl(4)-treated rat liver. Treatment with curcumin showed only mild sinusoidal dilatation while with BDMC-A there was only mild portal inflammation. The effect exerted by BDMC-A was found to be more promising than curcumin.     

Hepatic microsomal phospholipids in rats exposed intratracheally to coal fly ash

The effects of intratracheal administration of fly ash (50 mg/kg body weight, daily for 7 days) on hepatic microsomal phospholipid metabolism has been studied in rats using various phospholipid precursors, viz NaH₂ ³²PO₄, (methyl-¹⁴C)-choline, and (methyl-¹⁴C)-methionine. Fly ash administration significantly increased microsomal phosphatidylcholine (PC), and lysophosphatidylcholine (LPC). The incorporation of NaH₂ ³²PO₄ into total liver phospholipids, PC and Phosphatidyl ethanolamine (PE) was significantly increased in fly ash-treated rats as compared to the control. Fly ash administration also increased the incorporation of (methyl-¹⁴C)-choline into microsomal PC. Incorporation of (methyl-¹⁴C)-methionine into microsomal PC was not affected. Fly ash administration decreased the per cent distribution of arachidonic acid in PC and PE and increased that of oleic acid in PC and of linoleic acid in PE.     

Effect of black tea on lipid peroxidation in carbon tetrachloride treated male rats

This study examined the effects of black tea (Camellia sinensis L.) on lipid peroxidation and glutathione levels in carbon tetrachloride (CCl4)-treated male Wistar rats. Three groups of rats formed two control groups and one treatment group. The control groups were fed with a standard diet, while the black tea group were fed the standard diet plus 6% by weight dried black tea leaves. After two months, the rats in the black tea group and in one control group were administered a single dose of CCl4 (1 ml/kg, i.p.) and sacrificed two hours later. Rats in the other control group were administered olive oil in a similar fashion. Lipid peroxide levels in liver and plasma, glutathione (GSH) levels in liver and alanine transaminase (ALT) and aspartate transaminase (AST) activities in plasma were measured. Rats in the black tea group were found to have significantly decreased liver lipid peroxide levels, and ALT and AST activities compared with the rats in the CCl4-treated control group. In addition, liver glutathione levels were decreased in the black tea group. These data suggest that black tea attenuates CCl4-induced hepatic injury.     

Effect of black tea on lipid peroxide and glutathione levels in female rats

The effects of black tea (Camellia sinensis L.) on lipid peroxidation and glutathione (GSH) levels in carbon tetrachloride (CCl4)-treated female Wistar rats were examined. Two control groups and one treatment group were tested. The control groups were fed with a standard diet, while the black tea group was fed the standard diet plus 6% by weight dried black tea leaves. At the end of 2 months, a single dose of CCl4 (1 ml/kg, i.p.) in olive oil was administered to rats in one of the control groups and the black tea group. They were sacrificed after 2 hours. Rats in the other control group were administered olive oil in a similar fashion. Measurements were made of lipid peroxide levels in liver and plasma, glutathione levels in liver, and alanine transaminase (ALT) and aspartate transaminase (AST) activities in plasma. Liver lipid peroxide levels, plasma ALT and AST activities were significantly decreased in the black tea group compared with the CCl4-treated control group, while plasma lipid peroxide levels were not. These results are parallel to those previously found with Wistar male rats. Glutathione levels, however, were not significantly affected, in contrast to the data relating to male rats, either after CCl4 or black tea treatments. The results of our study add to the findings that black tea attenuates CCl4-induced hepatic injury but also indicates the susceptibility of glutathione levels to endocrinological effects.     

Ethanol-induced alterations in rat synaptosomal plasma membrane phospholipids. Relationship to changes in the phospholipid methyltransferases

The effects of ethanol ingestion on the lipids of the synaptic plasma membrane (SPM) have been measured and correlated with the time frame for the development of physical dependence. Alterations were observed in three of the phospholipid fractions: phosphatidylcholine (PC) increased, and the phosphatidylethanolamine (PE) and phosphatidylserine (PS) plus phosphatidylinositol (PI) fractions decreased. These alterations occurred after the animals showed signs of dependence. Because PC can be synthesized from PE by the methyltransferase pathway, synaptosomal methyl group incorporation was measured. Rats were fed ethanol for 6 days before an increase was observed in methyl incorporation, a shorter length of time than was necessary to demonstrate physical dependence or phospholipid alterations (10 to 14 days). After ethanol withdrawal, 7 days of control diet feeding were required for methyl group incorporation to return to control values. In vitro ethanol (10-250 mM) additions to the methyltransferase incubations resulted in a slight increase in methyl incorporation. These data suggest that synaptic membrane lipid alterations may be related to ethanol dependence and that changes in the PC/PE ratio may be the result of an increase in the incorporation of methyl groups into synaptosomal phospholipids.     

Vitamin A supplementation increases levels of retinoic acid compounds in human plasma: possible implications for teratogenesis

The concentrations of retinoic acid compounds were monitored by a newly developed highly sensitive HPLC procedure in plasma of six volunteers who received 833 IU vitamin A per kg body weight per day during a 20-day period. There was a significant increase of alltrans-retinoic acid (two-fold), 13-cis-retinoic acid (7-fold) and 13-cis-4-oxoretinoic acid (5-fold) over endogenous plasma levels of these retinoids. The same compounds had previously been found after treatment with the teratogenic drug isotretinoin (Roaccutan, Accutane). Our results raise the possibility that high vitamin A intake may carry a teratogenic risk attributable to increased levels of retinoic acid compounds generated from retinol by metabolic processes.The term vitamin A is used for retinol or retinyl esters