The Role of Alcohol Metabolism in the Effect of Ethanol on Protein Synthesis in Isolated Rat Hepatocytes

Rat liver parenchymal cells were isolated and incubated for 1–2 hr in a buffered salt solution. The addition of increasing concentrations of ethanol (10–105 mM| to the suspensions was accompanied by a dose-dependent reduction (5%-60%) of ¹⁴C-valine incorporation into medium and cell proteins. Ethanol metabolism by alcohol dehydrogenase (ADH) was maximal between 10 and 20 m/W ethanol and did not increase at higher ethanol concentrations. Four-methylpyrazole (4-MP) (0.5 m/W), which inhibited ADH. abolished the inhibitory effect of low concentrations of ethanol (8 m/W) on valine incorporation, while it could not prevent the. inhibition caused by higher concentrations of ethanol (16 and 65 m/W). D-Penicillamine (2 and 4 m/W), which complexes acetaldehyde, did not influence the inhibitory effect of ethanol on valine incorporation into protein. Additions of acetate (5 and 10 m/W) or sorbitol (3.5 and 5 m/W) were not able to mimic the effect of ethanol, as neither could reduction of medium pH from 7.4 to 7.0. Propanol (6–32 m/W) as well as tertiary butanol (5 and 10 m/W) inhibited valine incorporation into protein in a dose-dependent manner. When ethanol was added to hepatocytes prepared from animals fed ethanol for 6 wk, the same inhibition of valine incorporation into protein was found as for cells from previously untreated rats. It was concluded that the inhibition of valine incorporation into liver proteins, which previously has been shown to be due to reduced protein synthesis, may occur in two ways. Low concentrations of ethanol appear to exert its effect through ethanol metabolism, while probably a direct effect of ethanol (and other alcohols) becomes increasingly important as the alcohol concentration rises.     

Measurement of Protein Synthetic Activity by Determination of Peptidyl[3H]puromycin Formation in Liver Slices after Ethanol Administration

We investigated the utility of [3H]puromycin as an alternate and adjunct precursor to amino acids for measuring protein synthetic activity in rat liver slices. Slices were incubated in the presence of either [3H]puromycin or radiolabeled valine to compare the incorporation of these isotopic precursors into nascent hepatocellular proteins. Compared to liver slices from controls, comparable decreases in the incorporation of both [3H]puromycin and labeled valine were observed in experiments using slices from fasted rats and in slices preincubated with 25 mM ethanol. Radiolabeling of nascent polypeptides with either [3H]puromycin or labeled valine in liver slices from rats fed a liquid diet containing ethanol was also decreased compared to slices from pair-fed control and chow-fed animals. Our results demonstrated the validity of using [3H]puromycin to detect changes in protein synthetic activity under these conditions. The potential advantage of using [3H]puromycin for in vivo studies is discussed.     

Hepatic Protein Synthetic Activity in Vivo after Ethanol Administration

Hepatic protein synthetic activity in vivo was measured by the incorporation of [3H]puromycin into elongating nascent polypeptides of rat liver to form peptidyl-[3H]puromycin. Our initial experiments showed that saturating doses of [3H]puromycin were achieved at 3-6 mumol/100 g body weight, and that maximum labeling of nascent polypeptides was obtained 30 min after injection of the labeled precursor. Labeled puromycin was found to be suitable for measuring changes in the status of protein synthesis, since the formation of the peptidyl-[3H]puromycin was decreased in fasted animals and was increased in rats pretreated with L-tryptophan. [3H]Puromycin incorporation into polypeptides was then measured after acute ethanol administration as well as after prolonged consumption of ethanol which was administered as part of a liquid diet for 31 days. Acute alcohol treatment caused no significant change in [3H]puromycin incorporation into liver polypeptides. In rats exposed to chronic ethanol feeding, peptidyl-[3H]puromycin formation, when expressed per mg of protein, was slightly lower compared to pair-fed controls, but was unchanged compared to chow-fed animals. When the data were expressed per mg of DNA or per 100 g body wt, no differences in protein synthetic activity were observed among the three groups. These findings indicate that neither acute nor chronic alcohol administration significantly affects protein synthetic activity in rat liver. They further suggest that accumulation of protein in the liver, usually seen after prolonged ethanol consumption, is apparently not reflected by an alteration of hepatic protein synthesis.     

The Hepatoprotective Effect of Hepatic Stimulator Substance (HSS) Against Liver Regeneration Arrest Induced by Acute Ethanol Intoxication

Male Wistar rats were randomized to receive ethanol (2.5 ml/kg by gastric intubation every 8 hr; group I), equal volumes of isocaloric to ethanol sucrose solution (group II), or ethanol and HSS (100 mg/kg intraperitoneally 10 and 16 hr after partial hepatectomy; groups III and IV, respectively) for up to 96 hr after partial hepatectomy, with ethanol administration starting 1 hr prior to partial hepatectomy. Animals were killed at 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 60, and 96 hr after partial hepatectomy. The rate of liver regeneration was evaluated by the mitotic index in H&E-stained sections, immunochemical detection of Ki67 nuclear antigen, rate of [³H]thymidine incorporation into hepatic DNA, and liver thymidine kinase enzymatic activity. The biological activity of HSS in groups I and II rats was evaluated using a bioassay. Ethanol administration arrested liver regeneration during the first 32 hr after partial hepatectomy and suppressed HSS activity throughout the period examined. Liver regeneration progressed after 32 hr despite the low levels of HSS activity. HSS administration at 10 and 16 hr reversed liver regeneration arrest induced by ethanol. Acute ethanol administration induces cell cycle arrest during the first 32 hr after partial hepatectomy and suppression of HSS biological activity seems to contribute to this effect. HSS administration reversed the inhibitory effect of ethanol on liver regeneration and caused synchronized entrance of hepatocytes in the S phase of the cell cycle. HSS seems to participate in the network of growth factors controlling the G1/S cell cycle checkpoint.     

Acute Effect of Ethanol on Membranes of the Endoplasmic Reticulum and on Protein Synthesis in Rat Liver

The acute effect of ethanol on the membranes of hepatic endoplasmic reticulum, on the in vitro protein-synthetic activities of hepatic free and membrane-bound polyribosomes and on the plasma proteins of rats fasted overnight was investigated. Ethanol (0.75 g/100 g body weight) was tube-fed as a 50% (v/v) solution in saline 3 hr before sacrifice. Hepatic endoplasmic reticulum membranes from control and ethanol-treated rats were compared using the following techniques: (1) lactoperoxidase-catalyzed radioiodination of proteins and sodium dodecylsulfate-polyacrylamide gel electrophoresis, and (2) measurement of ¹⁴C-choline incorporation into membranes. Hepatic microsomal membranes from ethanol-treated rats incorporated in vitro less ^12BI into total proteins (as well as into the 55,000 molecular weight proteins) and incorporated in vivo less ¹⁴C-choline into microsomal membranes than membranes of control rats. Ethanol administration inhibited in vivo incorporation of "C-leucine or ¹⁴C-phenylalanine into liver protein and plasma albumin and globulin. The data also indicate that an acute dose of ethanol reduced the in vitro protein-synthetic activity of hepatic membrane-bound polyribosomes, while free polyribosomes were relatively unaffected.     

Hepatic Synthesis of Apoproteins of Very Low Density and High Density Lipoproteins in Perfused Rat Liver: Influence of Chronic Heavy and Moderate Doses of Ethanol

The effects of 6 weeks of heavy and moderate ethanol feeding to rats upon lipids and lipoprotein metabolism were determined. As compared to the control group, the heavy ethanol feeding resulted in the following changes: liver weight/kilogram body weight increased by 48% (p less than 0.001) with a concomitant 52% increase (p less than 0.001) in liver protein/kilogram body weight and a 2.75-fold (p less than 0.001) increase in liver total lipids/kilogram body weight. In contrast, liver DNA/kilogram body weight or per liver was not affected significantly. Plasma cholesterol and triglycerides were higher by 53% (p less than 0.01) and 77% (p less than 0.01), respectively. Liver cholesterol and triglycerides were 4.4-fold and 3.8-fold higher (p less than 0.001), respectively. Plasma total A1 was 1.72-fold higher (p less than 0.001), whereas there was no significant difference in plasma apo E levels between the two groups. However, plasma high density lipoproteins (HDl) apo E was 48% lower (p less than 0.02) while the very low density lipoproteins (VLDL) E was 2.15-fold higher (p less than 0.02). Hepatic total protein synthetic rate in the ethanol group was not significantly different from the control group. In contrast, labeled leucine incorporation into the total secretory proteins was inhibited by 36% (p less than 0.01) in ethanol-fed group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of acute ethanol administration on the intestinal absorption of endotoxin in rats

BACKGROUND: Endotoxin has been implicated in the pathogenesis and progression of alcoholic liver disease. Not only inactivation of reticuloendothelial function, which reduces clearance of endotoxin, but also an increase in absorption of endotoxin from the intestine may be involved in mechanisms of ethanol-induced endotoxemia. However, it is unclear how ethanol affects absorption of endotoxin from the intestine in vivo. METHODS: We gave 10 mg/kg of lipopolysaccharides to rats with water (group 1), 5% ethanol (group 2), or 20% ethanol (group 3) using an intubation tube to the stomach. Blood samples were collected and plasma endotoxin levels were measured. We used fluorescence spectrophotometer to examine permeability of the gut to macromolecules (fluorescein isothiocyanate-dextran; 4,000 Da [FD4] or 20,000 Da [FD20]). RESULTS: Plasma endotoxin levels were not different between group 1 (9 +/- 2 pg/ml) and group 2 (14 +/-3 pg/ml), whereas they significantly increased in group 3 with a peak at 60 min (87 +/- 35 pg/ml). Acute ethanol administration did not affect clearance of endotoxin in rats. Hemorrhagic erosions of the proximal small intestine with epithelial cell loss were observed in group 3 at 4 hr, but no significant histological change was observed at 30 min by light microscopy. Acute ethanol administration (20%) increased the permeability of the small intestine to FD4 and FD20 in 30 min when no hemorrhagic erosions of the proximal small intestine with epithelial cell loss were observed. CONCLUSIONS: Acute ethanol administration increases intestinal permeability before pathological changes are revealed by light microscopy. Acute ethanol ingestion, especially at high concentrations, facilitates the absorption of endotoxin from rats' small intestine via an increase in intestinal permeability, which may play an important role in endotoxemia observed in alcoholic liver injury.     

Effects of starvation, refeeding, and insulin on energy-linked metabolic processes in catfish (Rhamdia hilarii) adapted to a carbohydrate-rich diet

The effects of starvation and of a short period of refeeding on energy-linked metabolic processes, as well as the effects of insulin administration, were investigated in an omnivorous fish (catfish, Rhamdia hilarii) previously adapted to a carbohydrate-rich diet. Following food deprivation blood sugar levels declined progressively to about 50% of fed values after 30 days. During the same period plasma free fatty acid (FFA) concentration increased twofold. Starvation resulted in reduced concentrations of lipid and glycogen in the liver and of glycogen, lipid, and protein in white muscle. However, taking into account the initial and final concentrations of tissue constituents, the liver weight, and the large fractions of body weight represented by muscle, it could be estimated that most of the energy utilized during starvation derived from the catabolism of muscle lipid and protein. Refeeding starved fishes for 48 hr induced several-fold increases in the rates of in vivo and in vitro incorporation of [14C]glucose into liver and muscle lipid and of [14C]glycine into liver and muscle protein. Incorporation of [14C]glucose into liver glycogen was also increased. However; refeeding did not affect the incorporation of labeled glucose into muscle glycogen, neither in vivo nor in vitro. Administration of pharmacological doses of insulin to normally fed catfishes resulted in marked increases in the in vivo incorporation of 14C from glucose into lipid and protein in both liver and muscle. In contrast, labeled glucose incorporation into muscle glycogen was not affected by insulin and label incorporation into liver glycogen was actually lower than that in noninjected controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Ethanol on DNA, RNA, and Protein Synthesis in Rat Astrocyte Cultures

Brain growth retardation is a major feature of the fetal alcohol syndrome (FAS). Insulin and insulin-like growth factors (IGF-I and IGF-II) exert significant growth-promoting effects on the central nervous system (CNS). The present study examined the effects of ethanol and its interactions with growth factors on the incorporation of labeled precursors into DNA, RNA, and protein in primary astrocyte cultures prepared from term fetal rats. Cultures were exposed to ethanol for 18hr in serum-free medium before measuring nucleoside or amino acid incorporation into acid-precipitable cell constituents. Under basal conditions, ethanol induced dose-dependent changes in the rates of incorporation of tritiated thymidine, uridine, and valine. The fraction of the total thymidine uptake that was incorporated into DNA was reduced in the presence of 100 and 200 mM ethanol. Effects on uridine and valine incorporation paralleled cell uptake. Insulin (10(-6) M) and IGF-I (10(-9) M) increased (p less than 0.01) incorporation of radiolabeled thymidine, uridine, and valine. Analysis of variance indicated highly significant interactions between ethanol and the effects of growth factors on incorporation of both nucleosides and valine. Interference with the action of neurotrophic factors may be a significant factor in fetal brain growth retardation associated with maternal ethanol ingestion.     

Acute ethanol intoxication stimulates superoxide anion production by in situ perfused rat liver.

This study examines the generation of superoxide anion by the perfused rat liver after ethanol intoxication and acute endotoxemia to assess the potential importance of oxygen-derived free radicals in the ethanol-induced hepatic pathological condition. Hepatic superoxide anion production of 0.65 +/- 0.06 nmol/min/gm liver weight was measured 1 hr after ethanol infusion; it reached a peak value of 0.8 +/- 0.07 at 3 hr and was reduced to 0.11 +/- 0.01 by 7 hr. In a group of animals, 4-methylpyrazole was injected 5 min before the administration of ethanol to determine whether the metabolism of ethanol moiety is necessary for the observed effects. However, no significant inhibition of superoxide production was observed after 4-methylpyrazole administration. Introduction of ibuprofen into the perfused liver abolished superoxide anion production, suggesting that arachidonic acid metabolites may play an important role in superoxide generation under these conditions. Endotoxin, a potent activator of macrophages, has also been associated with increased superoxide release by the liver. Therefore the combined impact of ethanol and endotoxin on superoxide production by the liver was also examined. Acute ethanol intoxication inhibited the endotoxin-mediated superoxide anion generation by the perfused liver. These data indicate that the ethanol-mediated superoxide production and the ethanol-induced inhibition of the lipopolysaccharide-enhanced free-radical generation by the liver may have a pathophysiological significance in tissue injury and in resistance to infection.     

Effects of somatostatin-25 and urotensin II on lipid and carbohydrate metabolism of coho salmon, Oncorhynchus kisutch

Salmon (Oncorhynchus kisutch) somatostatin (sSS; 4 or 8 ng/g body wt) or synthetic Gillichthys urotensin II (UII; 2 or 4 ng/g body wt) were injected intraperitoneally into juvenile freshwater coho salmon. Both sSS and UII caused a dose-dependent increase in plasma free fatty acids (FFA) which diminished with time. sSS induced an initial (1 hr) transient hyperglycemia. By contrast, UII tended to induce hypoglycemia, this effect being significant 5 hr after injection of the higher dose. Both sSS and UII depressed plasma insulin titers 1 hr after injection. By 3 hr, the sSS-associated insulin depression was no longer observed. UII treatment induced a hyperinsulinemia which was present 3 and 5 hr after peptide administration. Although no decreases in liver total lipid concentration or in mesenteric fat total tissue mass were observed, lipolytic enzyme activity within each depot was significantly enhanced by both peptides. Neither sSS nor UII altered 3H2O incorporation into fatty acids or neutral lipids. However, enhanced lipogenesis, particularly by UII, was indicated by increased NADPH production resulting from glucose-6-phosphate dehydrogenase activity. Both sSS and UII enhanced glucose mobilization, as indicated by decreased liver glycogen content and increased liver glucose-6-phosphatase activity. UII, but not sSS, stimulated glycogen synthetase activity. These results suggest that both sSS and UII stimulate hyperlipidemia by enhancing depot lipase activity and that although both factors are potentially gluconeogenetic, sSS seems to be glycogenolytic and hyperglycemic, whereas UII may channel glucose to FFA synthesis.     

Protective effect of some vitamins against the toxic action of ethanol on liver regeneration induced by partial hepatectomy in rats

AIM： To investigate the effects of vitamins （A, C and E） on liver injury induced by ethanol administration during liver regeneration in rats. METHODS： Male Wistar rats subjected to 70% partial hepatectomy were divided into five groups （groups 1-5）. During the experiment, animals of Group 1 drank only water. The other four groups （2-5） drank 30 mL of ethanol/L of water. Group 3 additionally received vitamin A, those of group 4 vitamin C and those of group 5 received vitamin E. Subsequently serum alanine aminotransferase （ALT）, aspartate aminotransferase （AST）, albumin and bilirubin were measured colorimetrically. Lipid peroxidation （thiobarbituric-acid reactive substances, TBARS） both in plasma and liver was measured, as well as liver mass gain assessment and total DNA. RESULTS： Compared with sham group, serum AST and ALT increased significantly under ethanol treatment （43% and 93%, respectively, with P 〈 0.05）. Vitamin C and vitamin E treatment attenuated the ethanol-induced increases in ALT and AST activity. Ethanol treatment also decreased serum albumin concentration compared to sham group （3.1 ± 0.4 g/dL vs 4.5 ± 0.2 g/dL; P 〈 0.05）. During liver regeneration vitamins C and E significantly ameliorated liver injury for ethanol administration in hepatic lipid peroxidation （4.92 nmol/mg and 4.25 nmol/mg vs 14.78 nmol/mg, respectively, with P 〈 0.05）. In association with hepatic injury, ethanol administration caused a significant increase in both hepatic and plasma lipid peroxidation. Vitamins （C and E） treatment attenuated hepatic and plasma lipid peroxidation. CONCLUSION： Vitamins C and E protect against liver injury and dysfunction, attenuate lipid peroxidation, and thus appear to be significantly more effective than vitamin A against ethanol-mediated toxic effects during liver regeneration.     

In vivo and in vitro effects of growth hormone on the incorporation of [14C]leucine into protein of liver and muscle of the eel

In vivo administration of ovine GH (2 micrograms/g body wt) increased [14C]leucine incorporation into protein of the liver, skeletal muscle, and opercular muscle of hypophysectomized eels. Addition of ovine GH into the medium (5 micrograms/ml) slightly increased [14C]leucine incorporation into protein of liver slices during 5 hr in vitro incubation, but did not affect protein synthesis from [14C]leucine in opercular muscle. In vivo pretreatment with ovine GH (2 micrograms/g body wt) 48 hr prior to tissue preparation clearly increased [14C]leucine incorporation into protein of liver slices in vitro. However, no statistically significant change was observed for in vitro incorporation of [14C]leucine into protein of opercular muscle of hypophysectomized eels which had been previously treated with ovine GH (2 micrograms/g body wt). These results indicate that ovine GH has a protein anabolic action in the liver and muscle of the eel and that compared to mammals a rather long lag period is needed to elicit such protein anabolic actions of GH in these animals.     

Inhibitory effect of melatonin on diquat-induced lipid peroxidation in vivo as assessed by the measurement of F2-isoprostanes

Melatonin is a powerful antioxidant and free radical scavenger. A large body of in vivo and in vitro evidence shows that melatonin effectively inhibits membrane lipid peroxidation; this damage was based on the measurement of malondialdehyde and/or 4-hydroxynonenal levels. In the current study, for the first time using a more sensitive and specific biomarker, i.e. F2-isoprostanes, we investigate the effect of melatonin on diquat-induced lipid peroxidation in Fischer 344 rats. When diquat (40 mg/kg body weight) was intraperitoneally injected into rats, the levels of liver F2-isoprostanes were significantly increased at 1, 3, and 6 hr while plasma free F2-isoprostanes concentrations were augmented at 3, 6, and 12 hr after administration of the toxin. In addition, the plasma alanine aminotransferase activity level was measured as a parameter of hepatoxicity; the activity of this enzyme was augmented at 3, 6, and 12 hr after diquat administration when compared with levels of this constituent in untreated control rats. Pretreatment with melatonin (20 mg/kg) 30 min before diquat administration resulted in a significant reduction in both tissue and plasma F2-isoprostanes levels, and plasma alanine aminotransferase activity. These findings, using a sensitive and specific index of lipid peroxidation, show that the hepatoxicity of diquat, at least partially, is a consequence of reactive oxygen species-induced lipid damage. Melatonin's protective effects likely relate to its direct free radical scavenging ability and/or due to other antioxidative processes induced by the indole.     

依折麦布长期干预对LDLR＋/－仓鼠高脂血症的影响及其对肝脏脂代谢基因的调控

目的探讨依折麦布长期干预调控脂代谢的效果和对肝脏脂代谢基因的调控。方法雄性低密度脂蛋白受体杂合子(LDLR^+/-)仓鼠随机分为两组:空白对照组和依折麦布组[25 mg/(kg·d)]。动物高脂饮食同时给药20周后,收集血浆、肝脏等组织样本。分析血浆中总胆固醇(TC)、甘油三酯(TG)、总胆汁酸(TBA)、非酯化脂肪酸(NEFA)和谷草转氨酶(AST)水平;检测肝脏中TC和TG水平;借助KTA快速蛋白液相色谱系统分离脂蛋白组分并检测各组分的TC和TG水平;采用实时荧光定量PCR和Western blot分别检测脂代谢相关基因和蛋白的表达。结果依折麦布长期干预显著下调LDLR^+/-仓鼠血浆中的TC、TG、TBA、NEFA和AST水平以及载脂蛋白B(ApoB)蛋白表达水平,但对脂蛋白脂肪酶(LPL)的蛋白表达和活性以及前蛋白转化酶枯草溶菌素9(PCSK9)的蛋白水平无影响;在肝脏中,依折麦布显著降低了TC水平,但对TG无显著影响;在基因水平上,依折麦布显著上调肝脏中甾醇调节元件结合蛋白2(SREBP-2)和PCSK9的表达,同时下调了胆固醇7α羟化酶A1(CYP7A1)、三磷酸腺苷结合盒转运体G5(ABCG5)、ABCG8和肝X受体α(LXRα)的表达。结论在LDLR^+/-仓鼠中,依折麦布长期干预可显著降低高脂血症,并展现出对多种肝脏脂代谢相关基因表达调控的复杂性。     

Effects of chronic ethanol administration on hepatic glycoprotein secretion in the rat

The effects of chronic ethanol feeding on protein and glycoprotein synthesis and secretion were studied in rat liver slices. Liver slices from rats fed ethanol for 4-5 wk showed a decreased ability to incorporate [14C]glucosamine into medium trichloracetic acid-precipitable proteins when compared to the pair-fed controls; however, the labeling of hepatocellular glycoproteins was unaffected by chronic ethanol treatment. Immunoprecipitation of radiolabeled secretory (serum) glycoproteins with antiserum against rat serum proteins showed a similar marked inhibition in the appearance of glucosamine-labeled proteins in the medium of slices from ethanol-fed rats. Minimal effects, however, were noted in the labeling of intracellular secretory glycoproteins. Protein synthesis, as determined by measuring [14C]leucine incorporation into medium and liver proteins, was decreased in liver slices from ethanol-fed rats as compared to the pair-fed controls. This was the case for both total proteins as well as immunoprecipitable secretory proteins, although the labeling of secretory proteins retained in the liver slices was reduced to a lesser extent than total radiolabeled hepatic proteins. When the terminal sugar, [14C]fucose, was employed as a precursor in order to more closely focus on the final steps of hepatic glycoprotein secretion, liver slices obtained from chronic ethanol-fed rats exhibited impaired secretion of fucose-labeled proteins into the medium. When ethanol (5 or 10 mM) was added to the incubation medium containing liver slices from the ethanol-fed rats, the alterations in protein and glycoprotein synthesis and secretion caused by the chronic ethanol treatment were further potentiated. The results of this study indicate that liver slices prepared from chronic ethanol-fed rats exhibit both impaired synthesis and secretion of proteins and glycoproteins, and these defects are further potentiated by acute ethanol administration.     

Ethanol administration generates oxidative stress in the pancreas and liver,but fails to induce heat-shock proteins in rats

BACKGROUND: Heat-shock proteins (HSP) play an essential role in the sequestration and reparation of denatured cellular proteins. Because ethanol treatment can result in oxidative stress-induced protein damage, it is possible that expression of HSP is altered after ethanol consumption. Dose-response and time-course studies were performed to investigate whether acute and chronic intragastric ethanol administration can induce tissue damage, oxidative stress and expression of the heat-shock proteins HSP60 and HSP72 in the pancreas and liver of male Wistar rats. METHODS: Laboratory and morphological analysis of pancreatic and liver damage were investigated. The degree of oxidative stress was assessed by measurement of the reduced glutathione content, lipid peroxidation and protein oxidation. The levels of HSP were examined by western blot analysis. RESULTS: Ethanol administration dose- and time-dependently elevated the serum ethanol concentration and hepatic enzyme activities. Chronic ethanol treatment also resulted in morphological damage of the liver. We observed that acute and chronic ethanol consumption had markedly different effects on the oxidative parameters in the pancreas and liver. Acute ethanol administration caused oxidative stress in the liver, whereas there was no such effect in the pancreas. In contrast, chronic ethanol feeding resulted in oxidative stress in both the pancreas and the liver. Furthermore, neither acute nor chronic ethanol intake induced the synthesis of HSP, a major defense system against cellular damage in the examined organs. CONCLUSION: Ethanol administration generates oxidative stress in the pancreas and liver, but fails to induce HSP in rats.     

Tumor necrosis factor stimulates hepatic lipid synthesis and secretion

Previous studies have shown that tumor necrosis factor (TNF) administration acutely increases serum triglyceride levels and stimulates hepatic de novo fatty acid synthesis. We now demonstrate that 60-90 min after TNF administration the incorporation of glycerol into triglycerides in the liver is increased 57% in chow-fed rats. Additionally, the quantity of labeled lipid in serum is increased 96% in the TNF-treated animals. TNF also acutely increases hepatic lipid synthesis and the quantity of labeled lipids in serum in rats fed a high sucrose diet. Moreover, using the Triton WR-1339 method, from 1-2 h after TNF administration there is a 52% increase in total hepatic triglyceride secretion. In contrast, in animals fasted before TNF administration, the characteristic increase in serum triglyceride levels is not observed, and neither the incorporation of glycerol into hepatic lipids nor the quantity of labeled lipids in the circulation are increased. By 17 h after TNF administration the incorporation of glycerol into hepatic lipid and the quantity of labeled lipid in the serum are no longer increased. These results indicate that in addition to TNF acutely stimulating de novo fatty acid synthesis, TNF also acutely stimulates hepatic triglyceride synthesis. The increase in hepatic triglyceride synthesis leads to increased secretion of lipids into the circulation. These observations provide strong support for our hypothesis that a TNF-induced stimulation of hepatic lipid synthesis and secretion contributes to the TNF-induced hyperlipidemia.     

Deficiency in plasma protein synthesis caused by x-ray-incuded lethal albino alleles in mouse.

Plasma protein synthesis was studied in mice bearing x-ray induced lethal mutations at the albino locus. Newborn albino mutants showed a decrease in each of the three principal plasma proteins, albumin, alpha-fetoprotein, and transferrin, when compared with colored littermate controls. Incorporation of [14C]leucine into plasma proteins of the newborn albinos 30 min after injection was only 1/5 that of the controls, but incorporation into total liver protein was only slightly diminished. Incorporation of [14C]leucine into an albumin fraction obtained by immunoprecipitation from livers incubated in vitro in an amino acid mixture was also strongly diminished. Thus, the liver of 18-day-old albino fetuses incorporated into this fraction 1/3 and that of newborn albinos 1/8 as much as the controls, but in both cases the incorporation into total liver protein was only 25% less than in the respective controls. These results indicate that the rather severe structural abnormalities observed in the mutants in the endoplasmic reticulum and the Golgi apparatus are not associated with a general deficiency of hepatic protein synthesis. Instead the data from this and previous work show that the progressive deficiency from fetal life to birth involves certain specific proteins represented by several perinatally developing enzymes and by plasma proteins. It is suggested that the mutational effects observed in these mice are due to deletions involving regulatory rather than structural genes at or near the albino locus.     

Effects of methylprednisolone on protein synthesis and blood flow in the postischemic liver

The effects of methylprednisolone (MP) on hepatic protein synthesis and blood flow following liver ischemia were studied in rats. Ischemia was induced by occluding all blood vessels to the left and median liver lobes during 1 hr and the experiments were continued for 2 hr following reperfusion. Protein synthesis was studied by determining rate of leucine incorporation into proteins in incubated liver slices. Hepatic blood flow was measured by xenon washout technique. One group of animals received MP intravenously (30 mg/kg) before induction of liver ischemia; one group was given the same dose of MP after ischemia; control rats received saline. Protein synthesis was reduced to the same extent at the end of the ischemic period in rats pretreated with MP as in control animals. During reperfusion, however, protein synthesis was restored faster and more completely both in animals receiving MP before and after ischemia than in control rats. No effects of MP on blood flow or adenine nucleotides in liver tissue were found. This study confirms previous reports on beneficial effects of glucocorticoids in liver ischemia and demonstrates improvement of one important hepatocellular function in the postischemic liver following administration of MP.