Ethanol increases hepatic smooth endoplasmic reticulum and drug-metabolizing enzymes

An Update on Animal Models of Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is a significant global health concern and a leading cause of liver disease-related deaths. However, the treatment options are limited due to the lack of animal models that accurately replicate ALD pathogenesis. An ideal ALD animal model should have pathological characteristics similar to those of human ALD, with a clear pathological process and ease of drug intervention. Over the years, researchers have focused on developing ideal ALD preclinical animal models by testing various methods, such as ad libitum drinking water with ethanol, acute, single large doses of ethanol gavage, multiple alcohol gavages in a short period, the Lieber-DeCarli liquid diet feeding model, the intragastric infusion model, and the Gao-binge model. With the increasing occurrence of obesity and metabolic dysfunction-associated steatotic liver disease, a new category of metabolic and alcohol-associated liver disease (MetALD) is also emerging. Studies have investigated the combined effects of a high-fat diet combined with binge alcohol or drinking water containing ethanol to mimic MetALD. In addition to mice, other species such as rats, guinea pigs, zebrafish, and non-human primates have also been tested to establish ALD preclinical models. This review aims to summarize current animal ALD models, particularly the emerging MetALD models, with the hope of providing a valuable reference for establishing more effective animal models in ALD studies in the future.

Hepatic TM6SF2 Is Required for Lipidation of VLDL in a Pre-Golgi Compartment in Mice and Rats

BACKGROUND & AIMS

Substitution of lysine for glutamic acid at residu 167 in Transmembrane 6 superfamily member 2 (TM6SF2) is associated with fatty liver disease and reduced plasma lipid levels. Tm6sf2-/- mice replicate the human phenotype but were not suitable for detailed mechanistic studies. As an alternative model, we generated Tm6sf2-/- rats to determine the subcellular location and function of TM6SF2.

METHODS

Two lines of Tm6sf2-/- rats were established using gene editing. Lipids from tissues and from newly secreted very low density lipoproteins (VLDLs) were quantified using enzymatic assays and mass spectrometry. Neutral lipids were visualized in tissue sections using Oil Red O staining. The rate of dietary triglyceride (TG) absorption and hepatic VLDL-TG secretion were compared in Tm6sf2-/- mice and in their wild-type littermates. The intracellular location of TM6SF2 was determined by cell fractionation. Finally, TM6SF2 was immunoprecipitated from liver and enterocytes to identify interacting proteins.

RESULTS

Tm6sf2-/- rats had a 6-fold higher mean hepatic TG content (56.1 ± 28.9 9 vs 9.8 ± 3.9 mg/g; P < .0001) and lower plasma cholesterol levels (99.0 ± 10.5 vs 110.6 ± 14.0 mg/dL; P = .0294) than their wild-type littermates. Rates of appearance of dietary and hepatic TG into blood were reduced significantly in Tm6sf2-/- rats (P < .001 and P < .01, respectively). Lipid content of newly secreted VLDLs isolated from perfused livers was reduced by 53% (TG) and 62% (cholesterol) (P = .005 and P = .01, respectively) in Tm6sf2-/- mice. TM6SF2 was present predominantly in the smooth endoplasmic reticulum and endoplasmic reticulum-Golgi intermediate compartments, but not in Golgi. Both apolipoprotein B-48 and acyl-CoA synthetase long chain family member 5 physically interacted with TM6SF2.

CONCLUSIONS

TM6SF2 acts in the smooth endoplasmic reticulum to promote bulk lipidation of apolipoprotein B-containing lipoproteins, thus preventing fatty liver disease.

Thinking Outside the Box

A broad definition of preconditioning is "the preparation for a subsequent action." Mounting evidence demonstrates that novel remote preconditioning paradigms, in which protective stimuli experienced locally can capacitate systemic tolerance and enhanced cell viability upon exposure to ensuing cellular insults, have been largely successful in the field of cardiovascular ischemia/reperfusion injury. To ensure successful protective preconditioning, some models (including the uterus) have been demonstrated to activate the unfolded protein response (UPR), which is a cellular stress response controlled at the level of the endoplasmic reticulum. However, in the context of remote preconditioning, activation of these intracellular molecular pathways must result in the extracellular transmission of adaptive signals to remote targets. In our recently published manuscript, we have described the activation of the UPR in the pregnant uterine myocyte to be associated with increased uterine myocyte quiescence and normal gestational length. We hypothesize that ubiquitous uterine gestational stresses experienced in every pregnancy, which have been demonstrated in other systems to activate the UPR, may induce a robust paracrine dissemination of a uterine secretome, for example, glucose-regulated protein 78, with preconditioning-like properties. Furthermore, we speculate that the gestational stress-induced uterine secretome acts to promote both local and systemic tolerance to the ensuing gestational insults, allowing for the maintenance of uterine quiescence. In this context, preterm labor may be the result of a pregnant uterus experiencing a stress it cannot accommodate or when it is unable to host an appropriate UPR resulting in insufficient preconditioning and a diminished local and systemic capacity to tolerate pregnancy-dependent increases in normal gestational stress. This is highly attractive from a clinical viewpoint as we ultimately aim to identify local and systemic adaptations that may serve as preconditioning stimuli for use as a strategy to restore appropriate preconditioning profiles to prolong uterine quiescence in pregnancy.

Two-stage model of chemically induced hepatocellular carcinoma in mouse

The aim of this study was to develop an efficient and reproducible mouse model for hepatocellular carcinoma (HCC) research and assess the expression of two proto-oncogenes (c-myc and N-ras) and tumor suppressor gene p53 in the carcinogenic process. In this study, we found that diethylnitrosamine initiation with CCl4 and ethanol promotion could induce a short-term, two-stage liver carcinogenesis model in male BALB/c mice, the process of hepatocarcinogenesis including liver damage, liver necrosis/cell death, liver inflammation, liver proliferation, liver hyperplasia, liver steatosis, and liver cirrhosis and hepatocellular nodules, which mimicked the usual sequence of events observed in human HCC. We also identified that the increase in expression of the p53 gene is related to the proliferation of hepatocytes, whereas overexpression of the c-myc and N-ras genes is associated with hepatocarcinogenesis. This animal model may serve as a basis for recapitulating the molecular pathogenesis of HCC seen in humans.

The effect of ethanol on drug oxidations in vitro and the significance of ethanol-cytochrome P-450 interaction

The effect of ethanol on N-demethylation of aminopyrine in rat liver slices and in the microsomal fraction and on microsomal hydroxylation of pentobarbital and aniline was studied. With liver slices N-demethylation of aminopyrine was stimulated by 35-40% at low ethanol concentrations (2mm), whereas no stimulation occurred at high concentrations (100mm). With the liver microsomal fraction, an inhibitory effect was observed only at high ethanol concentrations (100mm). This was also observed with the other drugs studied. In agreement with these results, only at a high concentration did ethanol interfere with the binding of drug substrates to cytochrome P-450. Further, as previously reported, ethanol produced a reverse type I spectral change when added to the liver microsomal fraction. Evidence that this spectral change is due to removal of substrate, endogenously bound to cytochrome P-450, is reported. A dual effect of ethanol is assumed to explain the present findings; in liver slices, at a low ethanol concentration, the enhanced rate of drug oxidation is the result of an increased NADH concentration, whereas the inhibitory effect observed with the microsomal fraction at high ethanol concentration is due to the interference by ethanol with the binding of drug substrates to cytochrome P-450.

Ethanol-induced oxidative stress: basic knowledge

After a general introduction, the main pathways of ethanol metabolism (alcohol dehydrogenase, catalase, coupling of catalase with NADPH oxidase and microsomal ethanol-oxidizing system) are shortly reviewed. The cytochrome P(450) isoform (CYP2E1) specifically involved in ethanol oxidation is discussed. The acetaldehyde metabolism and the shift of the NAD/NADH ratio in the cellular environment (reductive stress) are stressed. The toxic effects of acetaldehyde are mentioned. The ethanol-induced oxidative stress: the increased MDA formation by incubated liver preparations, the absorption of conjugated dienes in mitochondrial and microsomal lipids and the decrease in the most unsaturated fatty acids in liver cell membranes are discussed. The formation of carbon-centered (1-hydroxyethyl) and oxygen-centered (hydroxyl) radicals during the metabolism of ethanol is considered: the generation of hydroxyethyl radicals, which occurs likely during the process of univalent reduction of dioxygen, is highlighted and is carried out by ferric cytochrome P(450) oxy-complex (P(450)-Fe(3+)O(2) (.-)) formed during the reduction of heme-oxygen. The ethanol-induced lipid peroxidation has been evaluated, and it has been shown that plasma F(2)-isoprostanes are increased in ethanol toxicity.

The influence of inducers on drug-metabolizing enzyme activity and on formation of reactive drug metabolites in the liver

A variety of environmental agents can affect the rate of drug biotransformation in the liver by induction of drug-metabolizing enzymes. Both phase I and phase II reactions (the first and second stages of drug metabolism) may be influenced, and epoxide hydrolase, glucuronosyl transferases and glutathione-S-transferases are examples of enzymes which, in addition to the cytochrome P-450-linked monooxygenase system, are readily inducible by environmental agents. Phenobarbitone and 3-methylcholanthrene are the most widely studied representatives of two major classes of inducers. Induction of hepatic drug-metabolizing enzymes is often associated with enhanced detoxification of drugs and other foreign chemicals that are metabolized by these enzymes. However, during recent years, the effect of induction on many compounds has been found to be the opposite, i.e. toxicity is increased. This is true for most hepatotoxic drugs and major groups of chemical carcinogens; experiments with carbon tetrachloride, bromobenzene and benzo[alpha]pyrene serve to illustrate this point in the present paper. It is concluded that the toxicological significance of induction of drug-metabolising enzymes may differ from one substrate to another, and that general conclusions about the beneficial or harmful effects of induction should not be drawn.

Acetaminophen hepatotoxicity: the first 35 years

The acetaminophen nomogram including its uses and limitations is discussed as well as the development of the N-acetylcysteine protocol. While it has taken many years to elucidate the genetic variability and true multiplicity of the cytochrome P450 "mixed function oxidase system" many publications early on looked at the enzyme system as a single entity. Numerous articles indicated that barbiturates, anticonvulsants, and others could induce "P450" and add to the toxicity of acetaminophen. It rapidly became apparent that just because "P450" was induced when measured as a whole, not all other substrates would have changed metabolic activity. The role of diet and ethanol induction and inhibition on CYP2E1, the enzyme of greatest interest for acetaminophen is multifaceted. The lack of enhancement of acetaminophen toxicity by phenytoin and in fact, the potential for reduction of toxicity with that agent is a good example of the evolution of our knowledge. Further complicating our understanding is the introduction of misleading terms such as "therapeutic misadventure" and other expressions of molecular intent. A critical understanding of the literature makes it clear that therapeutic doses of acetaminophen either alone or in the presence of inducers do not produce toxicity. While the community of clinical toxicologists is small, it needs to be more aggressive in making sure that physicians from other specialties and non-clinical toxicology colleagues understand the significance and implications of this science.

Effects of alcohol consumption on pharmacokinetics, efficacy, and safety of fluvastatin

Alcohol consumption is known to have beneficial effects on cardiac mortality, probably by increasing high density lipoprotein cholesterol (HDL-C). Alcohol also increases triglycerides and, in some studies, total cholesterol and low density lipoprotein cholesterol (LDL-C). Nothing is known, however, of the effects of alcohol on the pharmacokinetics and efficacy of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Consequently, 2 studies have been carried out to determine the effects of alcohol consumption on the pharmacokinetics and efficacy of the HMG-CoA reductase inhibitor fluvastatin. Firstly, the effects of acute alcohol consumption on a single, oral 40 mg dose of fluvastatin were examined in a reference-controlled, randomized, crossover study in 10 healthy volunteers. Measurements were made after ingestion of 70 g of ethanol diluted to 20% with lemonade and, following a 7-day period, after ingestion of lemonade alone (reference). The half-life (t1/2) of a single dose of fluvastatin was significantly reduced by acute alcohol consumption compared with reference, whereas the area under the time-concentration curve (AUC), peak concentration (Cmax), and time to peak concentration (tmax) did not differ from the reference group. The lipid profile, measured 8 hr after administration, did not differ significantly from baseline in the reference group, apart from a slight reduction in apolipoprotein (apo)-AI. Triglyceride levels increased with alcohol, probably due to impaired fatty acid oxidation. Surprisingly, total cholesterol and LDL-C fell significantly, possibly due to altered pharmacokinetics, as reflected by the lower t1/2.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ethanol on microsomal drug metabolism in aging female rats. I. Induction

The purpose of this study was to determine how aging affects the induction by ethanol or acetone of the hepatic microsomal monooxygenase system of female Fischer 344 rats. Young-adult, middle-aged and old rats (4, 14 and 25 months) were fed an ethanol-containing or control liquid diet for 15 days. Cytochrome P-450, cytochrome c reductase, aniline hydroxylase, nitrophenol hydroxylase, nitroanisole O-demethylase and benzphetamine N-demethylase activities were measured in hepatic microsomes. All of the drug metabolism activities except benzphetamine N-demethylase were 20-35% lower in old than in young-adult rats fed the control diet. In addition, the increase in drug metabolism produced by feeding the regular ethanol diet (36% of calories as ethanol) was 50-60% lower in the old rats. However, there was no difference in the magnitude of ethanol induction when ethanol intakes were matched. The effects of chronic acetone consumption (1.2g/day per kg body weight for 15 days) paralleled those of ethanol consumption, except that the extent of induction was greater with acetone. Acetone-induced levels of hepatic microsomal cytochrome P-450, nitrophenol hydroxylase, nitroanisole O-demethylase and aniline hydroxylase were similar in all three age groups. The results of this study indicate that induction of hepatic microsomal drug metabolism by ethanol or acetone is unaffected by the aging process.

Impaired hepatic elimination of paranitrophenol and its metabolites in the rat following chronic ethanol pretreatment

Chronic ethanol feeding has been shown to enhance hepatic microsomal drug oxidation in humans and in laboratory animals. However, the effects of chronic ethanol administration on drug conjugation are less conclusive. We have studied the effects of chronic ethanol feeding on (a) the conjugation and elimination of p-nitrophenol (PNP) by the isolated perfused rat liver, (b) the formation of PNP glucuronide by hepatic microsomal PNP-glucuronyltransferase in vitro and (c) the hepatic content of UDP-glucuronic acid (UDPGA). PNP elimination from the isolated perfused rat liver was best described as a combination of parallel saturable and first-order processes. Ethanol pretreatment did not influence the former but resulted in a 48% reduction in the rate of elimination by the latter. This was associated with a significant reduction in recovery of PNP-glucuronide from bile, but no change in concentrations of PNP glucuronide or sulfate in perfusate. Michaelis constants and Vmax for PNP-glucuronyltransferase in native and solubilized microsomes and UDPGA concentrations in liver were not influenced by ethanol pretreatment. These results suggest that chronic ethanol treatment reduces PNP elimination in the intact liver primarily via a reduction in the biliary excretion of PNP glucuronide without altering glucuronidation per se.

Accumulation of phenols and catechols in isolated mouse hepatocytes in starvation or after pretreatment with acetone

Conditions leading to the accumulation of unconjugated phenols and catechols were investigated in mouse livers. The formation of unconjugated hydroxylated products of added p-nitrophenol and aniline was investigated in isolated hepatocytes prepared from 48 hr fasted or fed mice or from fed mice after acetone pretreatment. 4-Nitrocatechol and p-aminophenol--the hydroxylated products of p-nitrophenol and aniline--were accumulated in cells prepared from fasting animals, while in cells prepared from fed mice these unconjugated derivatives were not detectable. The accumulation of 4-nitrocatechol and p-aminophenol was also shown in isolated hepatocytes prepared from acetone pretreated fed mice. Inhibition of glucuronidation by N6,O2-dibutyryl cAMP or by D-galactosamine increased the accumulation of 4-nitrocatechol upon addition of p-nitrophenol in cells prepared from fasted mice. Both 48 hr starvation and acetone pretreatment enhanced the activity of microsomal p-nitrophenol and aniline hydroxylase by 300% and 600%, respectively, whereas p-nitrophenol conjugation in isolated hepatocytes as well as in hepatocyte homogenates was decreased by about 80% after 48 hr starvation. Acetone pretreatment did not alter the rate of p-nitrophenol conjugation measured in liver homogenates. It is suggested that a shift from conjugation toward hydroxylation in starvation gives rise to the formation of hazardous metabolites.

Biochemical and immunochemical evidence for the induction of an ethanol-inducible cytochrome P-450 isozyme in male Syrian golden hamsters

The effects of ethanol and of phenobarbital pretreatment on hamster microsomal metabolism of aniline and p-nitrophenol have been investigated. Hydroxylation of both compounds was increased over 2-fold by ethanol pretreatment, whereas phenobarbital pretreatment had little effect on either activity. Ethanol pretreatment had no effect on the specific content of total cytochrome P-450, while phenobarbital pretreatment increased the specific content 1.6-fold. Comparison of the specific activities for aniline hydroxylation and p-nitrophenol hydroxylation of individual microsomal samples from control, ethanol-pretreated and phenobarbital-pretreated animals showed a high degree of correlation (r2 = 0.98) consistent with the involvement of the same site for catalysis of these two compounds. Antibody to rabbit ethanol-inducible cytochrome P-450 (isozyme 3a) inhibited over 80% of the aniline (high affinity) and p-nitrophenol hydroxylase activities of microsomes from ethanol-treated hamsters. A comparison of the antibody-inhibitable rates for both hydroxylase activities with microsomes from untreated, ethanol- or phenobarbital-pretreated hamsters suggested that an isozyme homologous to rabbit isozyme 3a (hamster cytochrome P-450alc) was induced in hamsters about 3.5-fold by ethanol and was unaffected by phenobarbital. The induction of hamster cytochrome P-450alc was confirmed by immunoblot analysis of hamster microsomes. A single protein with a molecular weight of approximately 54,000 was recognized by antibody to the rabbit isozyme. Quantification of the immunoblots demonstrated that the hamster isozyme was increased about 3-fold, in good agreement with the induction determined by a comparison of the antibody-inhibitable rates. The results indicated that, although there was no change in the total spectrally observable cytochrome P-450, there was a marked change in the distribution of the isozymes of cytochrome P-450, with an increase in the alcohol-inducible form after 28-day ethanol consumption by chow-fed hamsters. This isozyme can be readily monitored by either high-affinity aniline or p-nitrophenol hydroxylation or by Western immunoblot analysis and appears to be the ethanol-inducible form of cytochrome P-450 in hamsters.

Rapid in vitro formation of smooth endoplasmic reticulum aggregates within peptide-producing islet cells

We report here that heptanol (3.5 mM) induces in vitro a rapid formation of smooth endoplasmic reticulum aggregates (SERA) within isolated islets of Langerhans. SERA appeared after only 15 min of exposure to the alkanol and increased in number during the first 30 min of incubation. At that time, SERA represented 2% and 6% of the volume of B- and non-B-cells, respectively. Removal of heptanol resulted in the rapid disappearance of SERA, whereas reintroduction of the alkanol rapidly induced these structures again. SERA formation was seen in different types of endocrine and nonendocrine islet cells. In the insulin-producing B-cells, SERA formation was not modified by conditions known to alter the secretory activity and the microtubular-microfilament network or to inhibit protein synthesis. By contrast, SERA formation was inhibited by low temperature and by conditions depleting the energy sources of the cells. Similar observations were made in the presence of either octanol (1 mM) or nonanol (1 mM) but not of shorter chain alkanols, alkanes, oxidative derivates of either heptanol or octanol, and of other unrelated lipid-soluble compounds. Incubations in the presence of long-chain alkanols provide, therefore, a unique model to study in vitro the formation and disposal of smooth endoplasmic reticulum, as well as a system in which rapid membrane biogenesis is amenable to direct experimental testing.

Hydroxyl radical generation by microsomes after chronic ethanol consumption

The effect of iron and other compounds known to be toxic because of the production of oxygen radicals, e.g., paraquat and menadione on the generation of hydroxyl radicals (.OH) by microsomes from chronic ethanol-fed rats and their pair-fed controls was determined. In the absence of any additions, or in the presence of ferric-chloride, -ADP or -EDTA, microsomes from the ethanol-fed rats showed a 2-fold increase in the production of .OH. Paraquat and menadione increased the generation of .OH by microsomes from the ethanol-fed and the pair-fed controls to an identical extent and thus these promoters of oxidative stress were not any more effective in interacting with microsomes after ethanol treatment. Under all conditions, .OH generation was sensitive to inhibition by catalase, implicating H2O2 as the precursor of .OH, whereas superoxide dismutase was without any significant effect. A working scheme to accommodate aspects of the interaction of iron, menadione and paraquat with microsomes with the subsequent production of .OH is described. The fact that .OH generation by microsomes in the presence of several sources of iron such as unchelated iron or ferric-ADP is elevated after chronic ethanol consumption could contribute to the hepatotoxic effects of ethanol. Studies on iron metabolism by liver cells and the effect of ethanol on the disposition of this critical trace metal are needed to further evaluate the role of oxygen radicals in the actions of ethanol.

Possible ethnic difference in toluene metabolism: a comparative study among Chinese, Turkish and Japanese solvent workers

Toluene metabolism was studied in 192 Chinese workers in comparison with that in 130 Japanese and 17 Turks. Time-weighted average concentrations of toluene in the breathing zone of workers were measured utilizing passive dosimeters, and hippuric acid (HA) and omicron-cresol (omicron C) concentrations in shift-end spot urine samples by high-performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. Under similar exposure conditions, male Japanese excreted almost twice as much HA as male Chinese, although such difference was less marked between female Chinese and Japanese. In contrast, the excretion of oC did not differ between the two ethnic groups. The ratio of oC over HA was highest among Turkish workers followed by Chinese, and lowest among Japanese. Possible roles of differences in toxicogenetics as well as in life patterns were discussed.

Ethanol oxidation and toxicity: role of alcohol P-450 oxygenase

The isolation and characterization of ethanol-inducible rabbit liver microsomal cytochrome P-450, termed P-450 3a or P-450ALC, has provided definitive evidence for the role of this enzyme in alcohol oxidation. From findings on the distribution, substrate specificity, and mechanism of action of P-450ALC we have suggested "alcohol P-450 oxygenase" as a more biochemically accurate name than "microsomal ethanol-oxidizing system." The present review is concerned with studies in this and other laboratories on activities and inducers associated with this versatile enzyme. Numerous xenobiotics, including alcohols and ketones, nitrosamines, aromatic compounds, and halogenated alkanes, alkenes, and ethers, are known to undergo increased microsomal metabolism after chronic exposure of various species to ethanol. Diverse compounds and treatments may induce P-450ALC, including the administration of ten or more chemically different compounds, fasting, or the diabetic state. Whether a common mechanism of induction is involved is unknown at this time. As direct evidence that P-450ALC catalyzes numerous metabolic reactions, the purified rabbit enzyme has been used in a reconstituted system to demonstrate various metabolic transformations, including the oxidation of various alcohols, acetone, acetol, p-nitrophenol, and aniline, the dealkylation of substituted nitrosamines, the reductive dechlorination of carbon tetrachloride, carbon tetrachloride-induced lipid peroxidation, and acetaminophen activation to form the glutathione conjugate.

Hepatic microsomal mixed-function oxidase activity in ethanol-treated hamsters and its consequences on the bioactivation of aromatic amines to mutagens

Male golden Syrian hamsters were maintained on ethanol-containing liquid diets for 4 weeks, corresponding to an average daily intake of 17 g/kg body wt. The p-hydroxylation of aniline was markedly enhanced by this treatment while minimal effects were seen in benzphetamine N-demethylase and ethoxyresorufin O-deethylase activities; there was no change in the microsomal levels of cytochromes P-450. Hepatic microsomal preparations from the ethanol-treated hamsters were more efficient than controls fed isocaloric diets in converting 2-aminofluorene, 4-aminobiphenyl, benzidine and 2-acetylaminofluorene into mutagens in the Salmonella mutagenicity test. The same treatment had no effect on the metabolic activation of 2-naphthylamine and even inhibited the mutagenicity of 2-aminoanthracene. No increase was seen in the activation of the two polycyclic aromatic hydrocarbons, benzo[a]pyrene and 3-methylcholanthrene to mutagens and an inhibitory effect was seen with the former. The ethanol-induced increase in the mutagenicity of 2-aminofluorene was inhibited by 2-butanol but not by the hydroxyl radical scavenger dimethylsulphoxide. It is concluded that chronic ethanol ingestion modulates the bioactivation of aromatic amines and amides to mutagens, the effect being substrate dependent. This effect of ethanol may be catalysed by unique form(s) of cytochrome P-450 whose synthesis is induced by such treatment.

Influence of chronic ethanol consumption on hamster liver microsomal O-dealkylase activities and cytochrome b5 content

The effects of two different methods of administering ethanol to hamsters on liver microsomal cytochrome levels and the activities of ethoxyresorufin O-deethylase and p-nitroanisole O-demethylase have been examined. Administration of ethanol in liquid diets resulted in enhanced levels of cytochrome P-450, NADPH-supported aniline hydroxylase (Form I), and both NADPH- and NADH-supported p-nitroanisole O-demethylase. NADH-ferricyanide reductase was also increased. No change in NADPH-cytochrome c reductase or in the NADPH-supported rate of ethoxyresorufin O-deethylase was observed. In contrast, both NADH-supported ethoxyresorufin O-deethylase and cytochrome b5 levels were decreased. Administration of ethanol in the drinking water to chow-fed animals had no effect on total cytochrome P-450 levels; however, the rates of NADPH-supported aniline hydroxylase (Form I) and p-nitroanisole O-demethylase activity were increased. No changes in NADPH-cytochrome c reductase, NADH-ferricyanide reductase, or NADH-supported p-nitroanisole O-demethylase activity were noted. Cytochrome b5 levels were decreased as were both the NADPH- and NADH-supported rates of ethoxyresorufin O-deethylase. These data suggest that chronic consumption of ethanol by hamsters either in liquid diet form or as ethanol-water solutions to chow-fed animals lowers cytochrome b5 levels. When cytochrome b5 levels are lowered and total chromosome P-450 levels remain unchanged, the NADPH-supported rate of microsomal O-dealkylation of ethoxyresorufin is decreased. These data suggest that cytochrome b5 participates in the NADPH-supported microsomal O-dealkylation of ethoxyresorufin.

Liver microsomal drug metabolism in ethanol-treated hamsters

Administration of ethanol in drinking water to Syrian golden hamsters for 1-3 weeks caused alterations of microsomal cytochrome P-450-dependent monooxygenase activities in the liver accompanied by a slight elevation in cytochrome P-450 content. Ethanol treatment resulted in an increase in the activities for ethanol oxidation, aniline p-hydroxylation and dimethylnitrosamine N-demethylation. In particular, when dimethylnitrosamine was used as a substrate, the rate of formaldehyde formation was enhanced by 2- to 2.7-fold, while ethanol oxidation and aniline p-hydroxylation were increased by 1.5- to 2- and 1.2- to 1.3-fold, respectively. On the other hand, the activities of 7-ethoxycoumarin O-deethylase, benzphetamine N-demethylase and benzo[a]pyrene 3-hydroxylase were apparently decreased after ethanol treatment. These results for hamsters were significantly different from those reported for rats.

Biochemical basis of alcoholism: statements and hypotheses of present research

Experimental results and theoretical considerations on the biology of alcoholism are devoted to the following topics: genetically determined differences in metabolic tolerance; participation of the alternative alcohol metabolizing systems in chronic alcohol intake; genetically determined differences in functional tolerance of the CNS to the hypnotic effect of alcohol; cross tolerance between alcohol and centrally active drugs; dissociation of tolerance and cross tolerance from physical dependence; permanent effect of uncontrolled drinking behavior induced by alkaloid metabolites in the CNS; genetically determined alterations in the function of opiate receptors; and genetic predisposition to addiction due to innate endorphin deficiency. For the purpose of introducing the most important research teams and their main work, statements from selected publications of individual groups have been classified as to subject matter and summarized. Although the number for summary-quotations had to be restricted, the criterion for selection was the relevance to the etiology of alcoholism rather than consequences of alcohol drinking.

Duodenal gamma-glutamyltransferase activity in human biopsies: effect of chronic ethanol consumption and duodenal morphology

Gamma-glutamyltransferase activity was determined in duodenal biopsies, and in the sera of forty-six non-alcoholic and eighteen alcoholic patients with a daily alcohol consumption of more than 80 g. Additionally, duodenal morphology was examined in biopsy material obtained at the same time. In both alcoholics (P less than 0.05) and in non-alcoholics (P less than 0.001) the duodenal gamma-glutamyltransferase activity revealed a significant positive correlation with duodenal villus length. In addition, alcoholics exhibited a significant decrease in duodenal villus length (338 +/- 13 vs. 363 +/- 13 microns, P less than 0.01), and a significant increase in duodenal gamma-glutamyltransferase activity (13.0 +/- 1.4 vs. 8.4 +/- 0.6 mU mg-1 protein, P less than 0.01) when compared to controls. No significant correlation was found between duodenal and serum gamma-glutamyltransferase activity in alcoholics and non-alcoholics. During follow up of two patients, duodenal gamma-glutamyltransferase activity decreased and duodenal villus length increased after withdrawing alcohol. These data underline the damaging effect of alcohol on the duodenal mucosa and demonstrate that chronic alcohol intake reversibly effects duodenal gamma-glutamyltransferase. In addition, the small intestine appears of minor importance as an origin for the elevated serum gamma-glutamyltransferase activities seen in the alcoholic.

The production of 1,2-propanediol in ethanol treated rats

Chronic administration of ethanol in the most commonly used experimental diet (Lieber, C. S., and DeCarli, L. M. (1976) Fed. Proceed. 35, 1232-1236) resulted in the production of 1,2-propanediol within one week of initiation of alcohol feeding. After two weeks 1,2-propanediol levels were 8.8 +/- 1.6 nmol/ml in alcohol treated animals. No 1,2-propanediol was apparent in pair fed control animals at any time during this study. Consistent with the proposed mechanism of production of 1,2-propanediol in acetone treated rats (Casazza, J. P., Felver, M. E., and Veech, R. L. (1984) J. Biol. Chem. 259, 231-236), both liver acetone and acetol monooxygenase activities and blood beta-hydroxybutyrate were elevated in ethanol treated animals. Acetone and acetol monooxygenase activities were 0.118 +/- 0.016 and 0.110 +/- 0.016 umol/min/g liver after two weeks of ethanol treatment. Acetone and acetol monooxygenase activities in pair fed controls were 0.016 +/- 0.002 and 0.015 +/- 0.002 umol/min/g liver. beta-Hydroxybutyrate levels were highest after one week of treatment; 1.64 +/- 0.12 umol/ml in ethanol treated rats and 0.16 +/- 0.02 umol/ml in pair fed controls. Throughout this study serum acetol and 2,3-butanediol were less than the detection limits of these assays (less than 5 nmol/ml).

Immunochemical evidence for induction of the alcohol-oxidizing cytochrome P-450 of rabbit liver microsomes by diverse agents: ethanol, imidazole, trichloroethylene, acetone, pyrazole, and isoniazid

Isozyme 3a of rabbit liver microsomal cytochrome P-450, also termed P-450ALC, was previously isolated in this laboratory from animals administered ethanol or imidazole, and the purified cytochrome was shown to function in the reconstituted system as an oxygenase in catalyzing the oxidation of ethanol and other alcohols. Although liver microsomes from animals treated in various ways exhibit increased alcohol-oxidizing activity, evidence was not available as to whether this was due to enzyme induction or to other factors influencing the activity. Immunochemical quantitation of P-450 isozyme 3a has now been achieved by use of purified antibody to this cytochrome in NaDodSO4/PAGE/blotting and dot-blotting techniques. The specific content of isozyme 3a in liver microsomes was found to be increased from 2- to greater than 4-fold by administration of the following agents, in increasing order of effectiveness as inducers: isoniazid, trichloroethylene, pyrazole, ethanol, imidazole, and acetone. Isozyme 3a represents about 5% of the total P-450 in control animals and is increased to as high as 27% by acetone treatment. Isozyme 3a-dependent butanol-oxidation activity, determined by the inhibitory effect of antibody on the various microsomal preparations, was found to increase proportionally with increased content of this cytochrome.

Involvement of cytochrome b5 in the hepatic microsomal metabolism of benzo(a)pyrene

Ethanol consumption decreased the specific content of microsomal cytochrome b5 in both chow-and liquid diet-fed hamsters while cytochrome P450 levels were unchanged in chow-fed animals and increased in liquid diet-fed animals. Microsomes from animals receiving ethanol in their drinking water exhibited decreased rates of microsomal aryl hydrocarbon hydroxylase activity and postmitochondrial supernatant mediated mutagenicity of benzo(a)pyrene. In contrast, microsomes from hamsters receiving ethanol in liquid diets showed no changes in either of these two activities. When the observed rates of 7,8 and 9,10 diol formation per nmole P450 for chow-fed animals are plotted vs. the b5/P450 ratio a positive correlation was observed suggesting that cytochrome b5 participates directly in the microsomal metabolism of benzo(a)pyrene.

Differences in the duration of the enhancement of liver mixed-function oxidase activities in ethanol-fed rats after withdrawal

Liver microsomal mixed-function oxidase activities were determined in female Sprague-Dawley rats after 3 weeks of ethanol feeding and for up to 10 days after withdrawal. Ethanol (36% of total calories) was administered in a high fat liquid diet and was replaced isocalorically by carbohydrates in controls. Chronic ethanol feeding similarly enhanced both microsomal cytochrome P-450 content and benzphetamine N-demethylase activity, per mg of protein, and resulted in a disproportionate increase in both aniline hydroxylase and 7-ethoxycoumarin O-deethylase activities. A 6- to 7-day withdrawal period was apparently necessary for the overall disappearance of these effects of ethanol. Marked differences, however, were seen in the time courses of return of these variables to control levels, as also indicated by changes, during this period and specially during the first 24 hr after withdrawal, in the apparent molar activity of the microsomal fraction with the three substrates tested. The results were interpreted as indicating that the distinct ethanol-inducible cytochrome P-450 isozyme, with a high specific activity toward aniline, undergoes a very rapid turnover in liver microsomes. Induction of another form of cytochrome P-450, differing from the former by its slower turnover rate, would explain the induction by ethanol of 7-ethoxycoumarin O-deethylase activity. The withdrawal of ethanol was followed by a rapid but transient increase in benzphetamine N-demethylase activity above the ethanol-induced level, at a time when other activities were rapidly declining. This could suggest that the microsomal content of other cytochrome P-450 isozyme(s), with high specific activity toward this substrate, would also be temporarily altered during ethanol withdrawal. Important alterations in microsomal cytochrome P-450-dependent mixed-function oxidase activities occurred during the initial 24-hr period of withdrawal, even in the absence of a change in microsomal cytochrome P-450 content, indicating that the effects of chronic ethanol ingestion on hepatic drug-metabolizing enzyme activities may also be highly dependent on the proximity of ethanol intake.

Role of alcohol P-450-oxygenase (APO) in microsomal ethanol oxidation

The form of liver microsomal cytochrome P-450 induced by chronic administration of ethanol to rabbits, designated as P-450ALC or P-450 isozyme 3a, has been purified to homogeneity as judged by several criteria, including NH2- and COOH-terminal amino acid sequence determination. The reconstituted alcohol-P-450 oxygenase (APO) system containing P-450ALC and NADPH-cytochrome P-450 reductase catalyzes the oxidation of a variety of primary and secondary alcohols to aldehydes and ketones, including methanol, ethanol, n-propanol, n-butanol, 2-butanol, n-pentanol, and cyclohexanol. Other purified P-450 cytochromes, including isozymes 2, 3b, 3c, 4, and 6, are much less active than P-450ALC in the oxidation of alcohols. That P-450ALC functions in ethanol oxidation in liver microsomal membranes as well as in the reconstituted system was shown by immunochemical experiments involving inhibition by sheep anti-P-450ALC antibodies. We conclude that P-450ALC is the predominant ethanol-oxidizing cytochrome present after induction by chronic alcohol administration and that the other P-450 cytochromes have low but significant activity in both control and ethanol-induced animals.

Dendritic inclusions in the cerebellar granular layer after long term alcohol consumption in adult rats

Whorled multiplanal inclusions up to 1.5 micron in diameter were observed in dendrites of the cerebellar Golgi cells after 6 months of alcohol treatment, increasing in number with time. Inclusions are formed by apposed cytomembranes stacked parallel or in a twisted arrangement. The paired membranes merged into a dense, finely textured material. A close relationship with dendritic smooth endoplasmic reticulum is apparent. A correlation between chronic alcohol intake and the development of these inclusions is shown although, in common with many other types of neuronal cytoplasmic inclusions, their genesis and function remains to be determined.

Changes induced in human liver by long-term anticonvulsant therapy. Functional and ultrastructural data

The study reports functional and morphological findings in eight male subjects undergoing anticonvulsant therapy for periods from 20 days up to 15 years. All subjects showed an increased activity of the hepatic microsomal NADPH cytochrome c reductase and an increased amount of smooth membranes in hepatocytes. The enzymatic activity was higher in the first years of treatment. Quantitative ultrastructural analysis showed that a twofold increase of the smooth membranes of hepatocytes had already been reached after 20 days of therapy, with a modest additional increase occurring thereafter. Both enzymatic and structural changes appear to be related to therapy. In addition, abnormal lipofuscin-related cytoplasmic formations were present in the hepatocytes of five subjects. Such formations are thought to represent an accumulation of abnormal degradation products, possibly related to an interaction of the drug(s) metabolites with cellular components.

Alcoholic hyalin-containing hepatocytes--a characteristic morphologic appearance

We studied the morphologic appearance of alcoholic hyalin (AH)-containing hepatocytes in liver biopsies from 14 patients with alcoholic liver disease. Most hepatocytes had a characteristic appearance. The cells were swollen and hydropic with an intact cell membrane. The mitochondria had variable-sized cristae which were both shortened and elongated. The smooth endoplasmic reticulum was markedly decreased. The rough endoplasmic reticulum was bizarre, with detachment of the ribosomes that surrounded the AH. The hepatocytes that contained AH bodies had lost almost all the glucose-6-phosphate activity but had variable amounts of succinic dehydrogenase and diphosphopyridine nucleotide diaphorase activities. The neutrophils admixed with mononuclear cells attached themselves to the hepatocytes and then invaginated into the hepatocytic cytoplasm with focal lysis of the cell membrane mediated via the release of neutrophilic lysosomes. The distortion of protein-synthesizing organelles and decrease in glucose-6-phosphatase activity suggest that the AH-containing hepatocyte is metabolically decompensated. The final cell death may be related to the neutrophilic attack, rather than the metabolic derangement.

The effect of chronic alcohol feeding on lipid peroxidation in microsomes: lack of relationship to hydroxyl radical generation

Chronic alcohol feeding causes microsomal induction including increased generation of hydroxyl radicals. Ethanol induced liver injury may be mediated by lipid peroxidation for which hydroxyl radicals have been proposed as major mediators. Ethanol promotes lipid peroxidation when given acutely but also may serve as a hydroxyl radical scavenger. Therefore, we studied the acute and chronic effects of alcohol on microsomal lipid peroxidation and hydroxyl radical generation. Chronic alcohol feeding in rats increased microsomal generation of hydroxyl radicals but lipid peroxidation of endogenous lipid was inversely related to hydroxyl radical generation. Ethanol (50mM) had a slight inhibitory effect on hydroxyl radical production in peroxidizing microsomes, no effect on endogenous lipid peroxidation and enhanced the lysis of RBCs added as targets of peroxidation. Enhanced microsomal generation of hydroxyl radicals following chronic alcohol feeding is not an important mediator of lipid peroxidation.

Hepatotoxicity following the therapeutic use of antipyretic analgesics

The potential for hepatic injury associated with the therapeutic use of salicylates and acetaminophen has recently attracted considerable attention. About 300 cases have been reported in which elevated transaminase levels or other evidence of hepatic injury developed following treatment with salicylates. Review of the spectrum of abnormalities reveals a group of patients (4 percent) with symptomatic liver damage in whom progressive or chronic liver disease is a possibility with continued use of the drug. In a few patients in this group, jaundice developed; several had abnormal prothrombin times; 11 (70 percent) had transaminase values in excess of 500 units; and five patients (30 percent) had encephalopathy and/or Reye's syndrome. In several reports liver damage has also been associated with the use of acetaminophen in therapeutic or near-therapeutic dosages. Of 18 patients, nine appeared to have ingested acetaminophen in amounts approaching overdose. Of the remaining nine patients, six were alcoholics. In the entire group, only five patients did not have a history of alcohol abuse; in three, glutathione depletion was suggested as a possible explanation for hepatotoxicity. The association with alcoholism or glutathione depletion suggests that host susceptibility may play a critical role. In two patients, long-term use of acetaminophen resulted in liver injury suggestive of chronic active hepatitis, possibly on the basis of an idiosyncratic reaction. In a study of chronic liver disease, acetaminophen half-life was prolonged (168 percent) without accumulation at 4 g a day over five days. In a double-blind, two-week, cross-over study, no clinical or laboratory evidence of adverse effects was found. There is, therefore, no evidence that chronic liver disease increases the risk of hepatotoxicity following the administration of acetaminophen in therapeutic doses. Thus, acetaminophen is the preferred antipyretic analgesic in patients with liver disease. Salicylates should be avoided since many of the adverse effects associated with these drugs are similar to the complications of chronic liver disease.

Increased acetaminophen-induced hepatotoxicity after chronic ethanol consumption in mice

The effect of chronic ethanol consumption on acetaminophen (200, 400, and 600 mg/kg) toxicity was determined by maintaining mice for 10 days on diets consisting of chow and one of the following drinking solutions: 10% ethanol + 10% sucrose, 8% sucrose, or tap water. Toxicity as manifested by mortality, liver enlargement, and liver congestion was greatest in the ethanol-treated group. We suggest that the greater mortality was a result of the increased liver congestion and consequent hypovolemia. Despite the increased levels of cytochrome(s) P-450, covalent binding of [3H]acetaminophen reactive metabolite(s) to liver protein was not higher in ethanol-treated animals. This can be explained by the higher initial glutathione concentration and/or ability to replenish glutathione in the ethanol-treated group. We suggest that the enhancement of acetaminophen toxicity by ethanol is the result of an effect of ethanol on hepatocyte membranes which renders the cells more susceptible to toxic injury.

Ethanol interaction with drug acetylation in vivo and in vitro

The acute effect of ethanol on sulfadimidine or procainamide pharmacokinetics was studied in healthy drug-free volunteers. Ethanol treatment increased the elimination rate, as well as the amount of acetylated drug measured in blood and urine. No changes of apparent volume of distribution or renal drug clearance were found. In three out of seven slow acetylators tested, the rate of acetylation increased so noticeably after ethanol that they would otherwise have been classified as rapid acetylators. Using suspensions of isolated rat liver parenchymal cells, the effect of ethanol, acetate, citrate, pyruvate, and L(-)carnitine on acetylation of sulfanilamide and procainamide was studied. Ethanol treatment enhanced sulfanilamide acetylation, whereas the acetylation of procainamide was unchanged. Acetate, citrate, and pyruvate treatment enhanced the acetylation of both drugs. Acetate treatment increased both Km and Vmax of both sulfanilamide and procainamide acetylation. In rat liver homogenates, acetyl-CoA increased the rate of sulfanilamide acetylation in a dose-dependent manner.

Are HLA antigens important in the development of alcohol-induced liver disease?

The prevalences of 10 HLA-A and 16 HLA-B antigens were determined in 50 patients with alcoholic cirrhosis and 120 alcoholic patients without cirrhosis and compared with those in a control group of 550 healthy subjects from the same geographical area. B40 was absent in the patients with cirrhosis but was found in 18 (15%) of the patients without cirrhosis (p = 0.0087). No other association was noted. It is concluded that there is no good evidence to date of an association between HLA antigen state and susceptibility to alcohol-induced cirrhosis.

Increased urinary D-glucaric acid excretion by children living in an area polluted with tetrachlorodibenzoparadioxin (TCDD)

Extremely small doses of TCDD have been shown to induce hepatic microsomal enzymes in animals. Whether levels of environmental exposure to TCDD were sufficient to produce enzyme induction in man, has been investigated in Seveso, where in July 1976 explosion in a factory spread toxic substances, one of which was TCDD, to the surrounding area. The hepatic microsomal enzyme activity was assessed by estimating urinary d-glucaric acid (UGA) excretion in children 6-8 years old. In 31 children, urine samples were collected between August and December 1976; in 67 other children in February 1979. As a control group 60 children living in Busto Arsizio (a small industrial town near Milan) and 26 living Cannero (a non-industrialized village on Lake Maggiore) were chosen. In the first period of collection, children with chloracne (which is considered to be a characteristic manifestation of intoxication with chlorinated products), showed significantly increased levels of UGA compared with children without chloracne. In 1979, children living in the Seveso area showed a statistically significant enhancement of d-glucaric acid excretion compared to the control groups. In conclusion, this study demonstrates that many children living in the Seveso area have an increased activity of hepatic microsomal enzymes, since, although the urinary excretion of d-glucaric acid is only an indirect measure of enzyme activity, studies in man have indicated that it is both sensitive and quantitative. As far as the cause of this increase is concerned, since it is possible to exclude the influence of alcohol, contraceptives, phenobarbitone or other drugs, it is reasonable to conclude that TCDD, a potent inducer agent, could be responsible for this phenomenon.

Ethanol-induced increase in procainamide acetylation in man

1 The effect of ethanol on procainamide pharmacokinetics was studied in humans by two different experimental designs. In one, ethanol was given 1.5 h after taking the drug followed by hourly drinks, while in the other ethanol was given 2 h before and subsequently after taking the drug. 2 In both studies, ethanol caused a significant reduction of T1/2 and a significant increase in total clearance of procainamide, while the apparent volume of distribution of procainamide, as well as the renal clearance of both procainamide and N-acetylprocainamide were unaffected by ethanol treatment. 3 Ethanol treatment increased the percentage of N-acetylprocainamide measured in blood and urine and the ratio of AUCNAPA/AUCPA significantly. 4 The T1/2 and total clearance of procainamide was significantly different in slow and rapid acetylators.

Inhibition of liver regeneration by chronic alcohol administration

Liver regeneration is the common mechanism whereby a patient recovers form a liver injury. In the western world, ethanol is the single most important aetiological factor associated with liver disease, and it appears crucial to determine if ethanol interferes with liver regeneration. We studied the response to a 70% hepatectomy in 240 rats receiving a nutritionally adequate diet containing 36% of their calories as ethanol for three weeks and their pair-fed controls receiving a liquid diet where ethanol is isocalorically replace with carbohydrates. Criteria of liver regeneration were: incorporation of 3H-thymidine in hepatocyte DNA (cpm/10 microgram DNA) and number of hepatocyte labelled nuclei on autoradiography per 100 high power fields. Controls displayed the usual response with peak activity of liver regeneration at 24 hours. Consumption of ethanol was associated with a statistically significant reduction of liver regeneration by both criteria for up to 72 hours after a 70% hepatectomy and delayed the peak of regenerative activity by 24 hours. This inhibiting effect was not related to the presence of alcohol in blood nor to hepatic microsomal enzyme induction by ethanol nor to widespread necrosis of hepatocytes. This effect was reversible after one week of abstinence. This impairment of liver cell renewal by ethanol may be of major significance in the severity and outcome of alcohol-related liver injury.

Interrelationships between vitamin D3 and 25-hydroxyvitamin D3 during chronic ethanol administration in the rat

Vitamin D [D] depleted female Sprague-Dawley rats were fed for a period of 4 wk a D deficient diet containing 36% of total calories as ethanol while control animals received an isocaloric regimen where ethanol was substituted for by dextrins. In conjunction with the ethanol feeding 92 I.U. of [14C]-vitamin D3 [(14C)-D3] were administered by intragastric gavage 3 times 1 wk for 3 2/3 wk. At the end of the experiment, [14C]-D3 and [14C]-25-hydroxyvitamin D3 [(14C)-25(OH)D3] concentrations were analyzed in plasma, liver, striated muscle and adipose tissue. Body reserves in unchanged [14C]-D3 were significantly reduced by ethanol treatment as seen by 24%, 26%, and 59% lower plasma (p less than 0.02), muscle (p less than 0.001) and adipose tissue (p less than 0.001) [14C]-D3 concentrations in ethanol-treated compared to control rats. In contrast total plasma and liver [14C]-25(OH)D3 content were increased by 30% (p less than 0.05) and 55% (p less than 0.001) respectively. This increased liver and plasma [14C]-25(OH)D3 following ethanol treatment was not accompanied by a proportional [14C]-25(OH)D3 incorporation into muscle and adipose tissue. These results suggest that during steady state conditions 25(OH)D3 production is increased during chronic ethanol administration while the body pool in unchanged D3 is significantly lowered. These results also point out that in the rat plasma 25(OH)D concentrations are not a reliable guide for the determination of vitamin D status during chronic ethanol administration.

Drug metabolism in alcoholics

The effects of chronic use of alcohol on drug metabolism are dependent on many variables, which determine the final outcome. The degree of liver injury, the inducing effect of long-term alcohol use and also macromorphological changes connected with advanced stages of alcohol-induced liver injury are of importance. Alcohol may also affect the toxification of foreign chemicals by the liver, thus rendering an individual more susceptible to chemical-induced toxic reactions. It is not possible to predict drug-metabolizing capacity of an alcoholic from clinical history, liver histology or serum biochemistry, although generally correlations among these parameters and hepatic drug-metabolizing enzymes are statistically significant. Consequently, direct assays for drug metabolism, e.g. the elimination of a test drug (e.g. antipyrine) or the drug under study itself, or enzyme measurements in biopsy samples, are needed if one wants to pursue "tailor-made" drug therapy for an alcoholic.