Hepatic Alcohol Dehydrogenase Activity Research Articles

Dietary carbohydrate accelerates ethanol elimination, but does not alter hepatic alcohol dehydrogenase.

In naive animals the rate of ethanol elimination is dependent on the hepatic alcohol dehydrogenase activity. Carbohydrates have been shown to modify ethanol metabolism by a mechanism that has not been determined. In this study, adult female rats, fed chow diets supplemented with fructose or glucose in their drinking water for 10 days demonstrated significantly greater ethanol elimination rates (4.85 +/- 0.28 and 4.92 +/- 1.56 microM ethanol/min/g liver, respectively) than rats receiving water (3.65 +/- 0.29). The hepatic alcohol dehydrogenase activity of the fructose (1687 +/- 101 nM ethanol/min/g liver) and the glucose (1832 +/- 15)-supplemented rats were not significantly different from that of control rats (1845 +/- 160). Dietary carbohydrate supplementation, therefore, enhanced ethanol elimination, but did not alter the activity of alcohol dehydrogenase. Thus the changes in the ethanol elimination rate following carbohydrate loading were not the consequence of an alteration in hepatic alcohol dehydrogenase.

Determinants of Ethanol and Acetaldehyde Metabolism in Chronic Alcoholics

We have studied the factors determining the rate of ethanol and acetaldehyde metabolism in a group of 25 alcoholics with varying degrees of liver lesion (from normal liver to cirrhosis) and in six nonalcoholic cirrhotics. In alcoholics the ethanol metabolic rate was related to hepatic function, estimated either by the aminopyrine breath test (r = 0.70, p < 0.001) or the indocyanine green clearance (r = 0.76, p < 0.01), and was independent of the activity of hepatic alcohol dehydrogenase and hepatic blood flow. In nonalcoholic cirrhotics blood acetaldehyde was always below the detection limit (0.5 microM), but elevated levels were found in 14 out of the 25 alcoholics. Alcoholics with elevated blood acetaldehyde showed a significantly higher ethanol metabolic rate than alcoholics with undetectable acetaldehyde (120 +/- 17 mg/kg/hr vs 104 +/- 11 mg/kg/hr, p < 0.02), but no differences were observed in the activities of alcohol and aldehyde dehydrogenases. Peak blood acetaldehyde levels were directly related to the ethanol metabolic rate (r = 0.48, p < 0.02), but not to activities of hepatic alcohol or aldehyde dehydrogenases. These results indicate that in chronic alcoholics the main determinant of the ethanol metabolic rate is hepatic function, while the rise of blood acetaldehyde is mainly dependent on the ethanol metabolic rate. Alcohol and aldehyde dehydrogenase activities do not seem to be rate-limiting factors in the oxidation of ethanol or acetaldehyde.

Modulation of hepatic and renal alcohol dehydrogenase activity and mRNA by steroid hormones in vivo.

Alcohol dehydrogenase (ADH) catalyzes the flux-determining step in the oxidation of ethanol and probably also plays a role in the metabolism of steroid alcohols and retinoids. Five classes of ADH have been discovered to date (Ehrig et al., 1990). The class I enzyme is the major liver enzyme, which is also found in other tissues at lower levels. This class of ADH has been studied in greatest detail. The gene for class I ADH has been cloned from humans (Duester et al. 1986), mice (Zhang et al., 1987), and rats (Crabb et al., 1989). In vitro studies have identified promoter elements important for liver specific expression (C/EBP and HNF1 binding sites (Potter et al., 1991; Stewart et al., 1990a; Stewart et al., 1990b; Stewart et al., 1991; van Ooij et al., 1992)) as well as hormone response elements. There are glucocorticoid response elements in the promoter (Duester et al., 1986), and expression of the gene is activiated in hepatoma cells exposed to dexamethasone (Wolfla et al., 1988; Dong et al., 1988; Winters et al., 1990). Retinoic acid response elements are present in the mouse and human ADH3 gene (Duester et al., 1991), and transfection studies demonstrate retinoic acid responsiveness of the promoter. Androgens induced mouse kidney ADH many fold by an effect that is mainly transcriptional (Ceci et al., 1986; Felder et al., 1988). Other hormone responses are less well understood. Estradiol is reported to induce ADH activity in the kidney (Qulali et al., 1991; Dembic and Sabolic, 1982), but not liver, of rats, and thyroid hormone reduces liver ADH activity (Potter and Mezey, 1983; Mezey and Potter, 1981).

Effect of age and gender on in vivo ethanol elimination, hepatic alcohol dehydrogenase activity, and NAD+ availability in F344 rats.

It has been reported that aging strikingly decreases in vivo ethanol metabolism in F344 rats without major effects on hepatic alcohol dehydrogenase (ADH) activity. Because hepatic ADH activity is not always rate limiting in the oxidation of ethanol, we measured in vivo ethanol elimination rate (EER), hepatic ADH activity, and the hepatic-cytoplasmic and mitochondrial redox states after acute ethanol application in 2- and 12-month-old F344 rats of both sexes. In male, but not in female, animals EER decreased with age significantly, by 28% (P less than 0.01). The body-to-liver weight ratio was significantly increased in male (39.4 +/- 1.5 vs 46.5 +/- 2.0; P less than 0.05), but not in female, animals with age. Specific activity of ADH was not significantly changed by age, while the activity was significantly reduced with age in male, but not female, rats when related to body weight (5.1 +/- 0.4 vs 3.9 +/- 0.3 mumoles/100 g b.wt./min; P less than 0.05). The cytoplasmic, but not the mitochondrial (NAD+) to (NADH), ratio was significantly decreased with age in male livers (317 +/- 48 vs 793 +/- 128, P less than 0.05), while this was not the case in female livers. In summary, the data show a sex dependence of the effect of age on ethanol metabolism. The observed reduction in in vivo EER with age in male animals is due at least in part to an increased body-to-liver weight ratio, decreased hepatic ADH activity, and reduced availability of NAD+, the cofactor of the ADH reaction. The cause of this may be decreased transport of reducing equivalents through the mitochondrial membrane due to a lack of shuttle systems or a change in the physicochemical properties of the mitochondrial membrane, or decreased reutilization of NADH as NADPH resulting from a reduction of microsomal ethanol oxidation with age.

Oxidoreduction of butanol in deermice (Peromyscus maniculatus) lacking hepatic cytosolic alcohol dehydrogenase

In view of conflicting information in the literature regarding enzyme systems responsible for alcohol oxidation in deermice previously reported to lack hepatic alcohol dehydrogenase (ADH) activity, the reversibility of butanol oxidation was studied in vivo and in liver-perfusion systems. Mixtures of [1,1-2H2]ethanol and butanol were given intraperitoneally to deermice lacking (ADH-) or possessing (ADH+) ADH activity, followed by analysis of alcohols in blood by GC/MS. 2H exchange between the two alcohols was seen in all experiments. In ADH- deermice, the 2H excess of butanol increased steadily and reached 18 +/- 5% after 2.5 h. In ADH+ deermice, butanol was rapidly eliminated and the 2H excess was about 7% after 0.5 h. In similar experiments with rats, the 2H excess was about 40% for 2 h. Perfusions of livers from ADH- deermice with mixtures of unlabelled and 1-[2H]butanol showed significant but slow intermolecular hydrogen transfer at C1, indicating oxidoreduction catalyzed by a dehydrogenase. Slow reduction of butanal was observed in mitochondria from ADH- deermice. ADH activity with a pH optimum of 10 and Km for ethanol of 6 mM was detected in the inner mitochondrial membranes from rats and deermice. However, low rates of oxidation observed in experiments carried out with perfused livers and in vitro suggest that this enzyme system does not contribute significantly to alcohol oxidation in vivo. Thus, perfused liver from ADH- deermice appears to be a useful system for studies of ADH-independent oxidation of alcohols. The 2H exchange between the alcohols seen in vivo indicates that both ethanol and butanol are substrates for a common extrahepatic dehydrogenase in ADH- deermice.

Comparison of rat pulmonary and hepatic cytosolic alcohol dehydrogenase activities

The liver is the major organ responsible for ethanol oxidation, and alcohol dehydrogenase (ADH) is the main enzyme involved. There is limited evidence suggesting the involvement of the lung in ethanol metabolism. To determine the degree to which pulmonary ADH plays a role in ethanol metabolism, ADH activity was measured spectrophotometrically using hepatic and pulmonary cytosolic fractions prepared by differential centrifugation and Sephadex G-50 column chromatography. Apparent Km values for hepatic and pulmonary ADHs were determined. Inhibition constants were calculated using 4-methylpyrazole. The ADHs were characterized by examining the influence of pH on enzyme activity. Pulmonary ADH activity was much lower at near neutral pH than at pH 9.0 or 10, whereas hepatic ADH activity was also pH dependent but was significantly higher. Pulmonary ADH is less sensitive to inhibition by 4-methylpyrazole than is hepatic ADH, as evidenced by a 1000-fold higher Ki. Pulmonary ADH would be expected to make only a minor contribution to ethanol metabolism in vivo.

Lowering and delaying actions of bovine bile on plasma ethanol levels in rats.

The effects of bovine bile (50-400 mg.kg-1 BW) on plasma ethanol levels in male rats (6-8 weeks old) were examined. Bovine bile decreased and delayed the peak of plasma ethanol concentration: a dose response to bovine bile was observed in the concentration and time to maximum concentration of ethanol but no change in disappearance rate. These phenomena were observed in two conditions: 1) oral administration of bovine bile before oral intubation of ethanol (1.0 g.kg-1 BW) and 2) simultaneous oral administration of bovine bile and ethanol. Similar responses were obtained in taurocholic acid. No changes in hepatic alcohol and aldehyde (low Km and high Km) dehydrogenase activities were observed. The remaining rate of ethanol in stomach was significantly higher with administration of bovine bile. A negative correlation between the maximum ethanol concentration and the remaining rate of ethanol in stomach was found. The intestinal absorption rate of ethanol decreased significantly in the presence of bovine bile. These results suggest that the delay of the gastric emptying and/or the decrease of the intestinal absorption rate of ethanol are major mechanisms for the decreasing and delaying effects on plasma ethanol by bovine bile. The present paper also suggests that bile acids such as taurocholic acid may participate in the lowering and delaying actions on the peak of plasma ethanol concentration by bovine bile.

Influence of acid-secretion blockers on gastric and hepatic alcohol dehydrogenase in rat.

The effects of Cimetidine, Ranitidine, and Omeprazole on gastric and hepatic alcohol-dehydrogenase (ADH) activity was studied in rat. Two apparent values for Km were found for gastric ADH (220 mmol l-1 and 1043 mmol l-1 respectively) and one for hepatic ADH (0.54 mmol l-1). Cimetidine was shown to exert an uncompetitive inhibition of low Km gastric ADH with a Ki of 0.167 mmol l-1 and a competitive inhibition of high Km gastric ADH with a Ki 2.3 mmol l-1. Ranitidine was found to present non-competitive inhibition only on low Km gastric ADH with a Ki of 12 mmol l-1. Omeprazole affects only low Km gastric ADH with a Ki of 5.6 mmol l-1 and presents a linear-mixed type of inhibition. Hepatic ADH was shown to be competitively inhibited only by Cimetidine with a Ki of 6.0 mmol l-1 whereas no inhibition for either Ranitidine and Omeprazole was observed. These results confirm the inhibitory action of Cimetidine on both gastric and hepatic ADH; Ranitidine and Omeprazole show minor effects on ADHS activity and probably on first-pass metabolism.

Liver damage, voluntary alcohol intake and brain histamine

Liver dysfunction induced by protocaval anastomosis (PCA) in the rat is associated with a great reduction of hepatic alcohol and aldehyde dehydrogenase activities. Despite this, PCA rats voluntarily drank more alcohol than unoperated rats. When subjected to forced alcohol consumption, shunted rats maintained their exaggerated voluntary alcohol intake whereas unoperated rats developed aversion to alcohol. Hypothalamic levels of both histamine and histidine were very high in PCA rats. When these rats were chronically exposed to alcohol, there was a slight decrease in hypothalamic histidine concentration and consequently a lower histamine content. Chronic exposure to alcohol did not, however, influence hypothalamic tissue levels of histamine or histidine in unoperated rats. In both groups, chronic alcohol treatment exerted a stimulatory effect on hepatic alcohol metabolizing enzymes.

Alcohol Preference and Hepatic Alcohol Dehydrogenase Activity in Adult Long‐Evans Rats is Affected by Intrauterine Sibling Contiguity

Alcohol preference and hepatic alcohol dehydrogenase activity in adult rats are known to be sexually dimorphic. Intrauterine sibling contiguity (the intrauterine position of a fetus relative to adjacent siblings of the same or opposite sex) alters selected reproductive, behavioral and enzymatic sexual dimorphisms via intersibling sex hormone transfer. We postulated that sibling contiguity would affect alcohol preference and hepatic alcohol metabolism in adult rats. The results of our study demonstrate that adult mMm male Long-Evans rats (genetic male rat developing in utero between two male siblings) had significantly lower ethanol preference, attained higher blood alcohol levels after standard ethanol "challenge" doses and had significantly lower hepatic alcohol dehydrogenase activity than either male siblings developing in utero between two females (fMf) or genetic females developing between two males or between two females (mFm or fFf). Hepatic cytosolic aldehyde dehydrogenase activity was higher in adult female than male rats regardless of nearest neighbor siblings. It is suggested that the differences in ethanol preference and hepatic alcohol dehydrogenase activity between the adult mMm and fMf male rats is due to differences in prenatal hormonal environment which can modulate sexual dimorphisms in alcohol intake and metabolism in the adult.

HEPATIC TRANSMETHYLATION AND BLOOD ALCOHOL LEVELS

Golden Syrian hamsters that have elevated hepatic alcohol dehydrogenase activity were divided into four groups and group-fed on four different liquid diets for five weeks. Group I was fed a control diet formulated for hamsters. Group II was fed the control diet containing 20 micrograms of 4 methylpyrazole per litre. Group III was fed the hamster ethanol liquid diet (ethanol amounting to 36% of total calories). Group IV was fed the ethanol diet to which 4-methylpyrazole (20 micrograms/litre) was added. Groups I, II and III were group-fed the amount consumed by Group IV on a daily basis. Upon killing the animals, blood alcohol levels were found to be elevated in Group IV but not in Group III. Hepatic methionine synthetase (MS) was inhibited in Group IV. Betaine-homocysteine methyltransferase was induced in this group to compensate for the MS inhibition and liver betaine was lowered reflecting this induction. None of these changes were seen in Group III. Since none of the animals showed an aversion to their respective diets and gained weight normally, these data indicate that it was the elevated blood levels of ethanol rather than nutritional factors that were related to the changes in methionine metabolism.

Hepatic alcohol dehydrogenase activity in alcoholic subjects with and without liver disease.

Alcohol dehydrogenase activity was measured in samples of liver tissue from a group of alcoholic and non-alcoholic subjects to determine whether decreased liver alcohol dehydrogenase activity is a consequence of ethanol consumption or liver damage. The alcoholic patients were classified further into the following groups: control subjects with no liver disease (group 1), subjects with non-cirrhotic liver disease (group 2), and subjects with cirrhotic liver disease (group 3). The non-alcoholic subjects were also divided, using the same criteria, into groups 4, 5, and 6, respectively. The analysis of the results showed no significant differences when mean alcohol dehydrogenase activities of alcoholic and non-alcoholic patients with similar degrees of liver pathology were compared (groups 1 v 4, 2 v 5, and 3 v 6. Alcohol dehydrogenase activity was, however, severely reduced in patients with liver disease compared with control subjects. Our findings suggest that alcohol consumption does not modify hepatic alcohol dehydrogenase activity. The reduction in specific alcohol dehydrogenase activity in alcoholic liver disease is a consequence of liver damage.

Hepatic alcohol dehydrogenase activity in chick hepatocytes towards the major alcohols present in commercial alcoholic beverages: Comparison with activities in rat and human liver

We have compared hepatic alcohol dehydrogenase activities in chick, rat and human liver with the major alcohols in commercial alcoholic beverages. 1. 1. Chick and rat hepatic alcohol dehydrogenase was greater when assayed at a physiological pH in buffer containing chloride ions, as compared with the activity in pyrophosphate buffer at alkaline pH. 2. 2. In contrast to reports of instability of ADH to freezing, we found the enzyme from all three species stable to freezing in 0.25 M sucrose. 3. 3. Rat liver enzymatic activity was unstable in the presence of substrate, where as that of chick and human was not. 4. 4. For all three species, the K m of hepatic ADH for substrate decreased with increasing chain length of alcohols. In both chick and human samples, the V max values for the higher chain alcohols were similar to that with ethanol, while in rat samples, ADH activity was dramatically lower with the higher chain alcohols compared to ethanol.

Developmental profile of hepatic alcohol and aldehyde dehydrogenase activities in long-sleep and short-sleep mice

Ethanol is metabolized primarily in the liver by a cytosolic alcohol dehydrogenase (ADH). The product, acetaldehyde, is metabolized to acetate by nonspecific aldehyde dehydrogenases (AHD). Mouse liver contains five major constitutive AHD isoenzymes: mitochondrial high K m (AHD-1), mitochondrial low K m (AHD-5), cytosolic high K m (AHD-7), cytosolic low K m (AHD-2) and microsomal high K m (AHD-3). The Long-Sleep (LS) and Short-Sleep (SS) mice differ in their sleep time response to ethanol as early as 10 days of age, and this difference increases with increasing age. Age- and genotype-related differences in metabolism could account for the pattern of responses seen in these mice. We measured the activity of hepatic ADH and the five AHD isoenzymes in LS and SS mice from 3 days of age to adulthood to determine if there were differences in the developmental profiles of these enzyme activities. We found no sex differences in the developmental profile of either ADH or AHD, and the LS and SS mice have nearly identical ADH and AHD activities with the possible exception of the high K m mitochondrial enzyme activity between days 3 and 6, and the low K m mitochondrial enzyme between days 28 and 32. Thus, it appears that differences in ethanol or acetaldehyde metabolism do not contribute significantly to the differential sensitivity to ethanol between young LS and SS mice or to the differential sensitivity between young and adult mice.

Selective mouse breeding for short ethanol sleep time has led to high levels of hepatic aromatic hydrocarbon (Ah) receptor

Following a selective breeding program of heterogeneous mice for more than 30 generations, SS (“short sleep”) and LS (“long sleep”) lines have been developed on the basis of their sleep times when challenged with a single intraperitoneal dose of ethanol. The aromatic hydrocarbon responsiveness ( Ah) locus encodes the Ah receptor, which regulates the induction of certain drug-metabolizing enzymes by polycyclic aromatic compounds such as 3-methylcholanthrene and tetrachlorodibenzo- p-dioxin. The C57BL/6 inbred mouse strain (B6; Ah b/ Ah b) has a high-affinity Ah receptor, while the DBA/2 inbred mouse strain (D2; Ah d/ Ah d) has a low-affinity Ah receptor. We show here that the SS inbred mouse line exhibits markedly elevated hepatic levels of the high-affinity Ah receptor, while the LS outbred mouse line contains the low-affinity Ah receptor. Among progeny of (B6D2)F 1 × D2 backcross, the b/ d heterozygote (having the high-affinity Ah receptor) was found to be several times more resistant than the d/ d homozygote to a single dose of intraperitoneal ethanol. The D2.B6- Ah b congenic line is also several times more resistant to intraperitoneal ethanol than the B6.D2- Ah d congenic line. We found that the waking blood ethanol levels are the same in b/ d and d/ d mice, suggesting that the relative ethanol resistance in b/ d mice cannot be explained on the basis of a difference in central nervous system sensitivity. There are no differences between SS and LS mice or between b/ d and d/ d mice with regard to (i) blood acetaldehyde levels after a single intraperitoneal dose of ethanol, or (ii) hepatic alcohol dehydrogenase activities. There is a difference in the rate of ethanol elimination: SS more rapid than LS; b/ d more rapid than d/ d. Although SS mice have lower hepatic aldehyde dehydrogenase activities (cytosolic, mitochondrial low- K m ; and mitochondrial high- K m forms) than LS mice, b/ d and d/ d do not show this difference. These data suggest that a selected mouse breeding program, based on resistance to a single intraperitoneal dose of ethanol, selects concurrently for the hepatic high-affinity Ah receptor. This selective advantage cannot be explained on the basis of changes in alcohol dehydrogenase or aldehyde dehydrogenase activities and might provide insight into the nature of the endogenous ligand for the Ah receptor.

Decreased in vivo rate of ethanol metabolism in the suckLing rat.

Blood concentrations of ethanol and acetaldehyde were determined in suckling rats after a single oral ethanol gavage. These results were compared with the hepatic activities of alcohol and aldehyde dehydrogenase. After intragastric administration of 3 g/kg body weight of ethanol, ethanol concentrations were much higher in suckling rats than in adult animals, especially at 90, 120, and 180 min after its administration. In addition, acetaldehyde concentrations were undetectable in suckling rats as opposed to adult rats, in whom micromolar concentrations were detected. Thus, 5- to 30-day-old rats seem to have a limited capacity for in vivo ethanol metabolism. The analysis of hepatic alcohol dehydrogenase activity revealed that it was very low at birth and it increased progressively with time attaining adult levels after 20 days of life. The alcohol dehydrogenase activity present in the liver of suckling rats presented similar Km values and sensitivity to pyrazole as adult rat liver. Thus, the pattern of in vivo ethanol elimination during the suckling period is not explained by hepatic alcohol dehydrogenase activity. Whether that diminished ethanol metabolism is due to slower intestinal ethanol absorption, different ethanol distribution in the body, or diminished hepatic capacity for NADH reoxidation remains to be studied. At birth, hepatic aldehyde dehydrogenase activity was low and it increased reaching adult levels during the suckling period. Adult levels for the component of low Km were attained earlier than for the component of high Km. The low affinity hepatic aldehyde dehydrogenase component in the newborn was different from that in the adult as assessed by kinetic studies and by its sensitivity to disulfiram.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of aging on in vivo and in vitro ethanol metabolism and its toxicity in F344 rats

To investigate the effect of aging on ethanol metabolism, 24 male and female F344 rats aged 2 and 12 mo that were fed a laboratory diet received ethanol (1.2 and 2.5 g/kg body wt) intraperitoneally. In male rats, in vivo ethanol elimination significantly decreased according to age both at high (436 ± 38 vs. 294 ± 27 mg/kg h; p < 0.01) and low (365 ± 19 vs. 261 ± 8 mg/kg · h; p < 0.01) blood ethanol concentrations. Age did not influence the specific activity of hepatic or gastric alcohol dehydrogenase, whereas the activity was significantly decreased with age in the liver (p < 0.05) and in the stomach (p < 0.001) when related to body weight. In addition, the activity of the hepatic microsomal ethanol oxidizing system decreased significantly according to age (8.7 ± 0.5 vs. 6.00 ± 0.3 nmol/min · mg micr. protein; p < 0.001). To study the response of ethanol-metabolizing enzymes to chronic ethanol ingestion, 2- and 19-mo-old male F344 rats were pair-fed nutritionally adequate liquid diets containing 36% of total calories either as ethanol or isocaloric carbohydrate for 3 wk. In this experiment specific alcohol dehydrogenase activity was not significantly affected by age, whereas the hepatic microsomal function estimated by the determination of cytochrome P450, microsomal ethanol oxidizing system, and aniline hydroxylation as well as hepatic mitochondrial low Km-acetaldehyde dehydrogenase activity was found to be markedly depressed with age (p < 0.01). Chronic ethanol consumption increased microsomal enzyme activities in older rats to levels comparable to those observed in young animals prior to ethanol administration. Chronic ethanol feeding also resulted in an increased hepatic fat accumulation, which was significantly enhanced in older rats. In contrast to male rats, in vivo ethanol metabolism was practically identical for 2- and 12-mo-old female rats. These data demonstrate an enhanced toxicity of alcohol in older compared to younger male but not female rats associated with a delay in alcohol elimination both at high and low ethanol blood concentrations and a decrease in ethanol- and acetaldehyde-mptabolizing enzyme activities.

Kinetic disposition of ethanol in the neonatal piglet and hemodynamic effects in the presence and absence of 4-methylpyrazole

The hemodynamic effects of acute ethanol intoxication and the kinetic disposition of ethanol are reported for the first time in neonatal piglets under nitrous oxide anesthesia. Two hours after a single dose of ethanol (1.4 g/kg), blood pressure decreased from 76 ± 4 to 71 ± 4 mm Hg (p < 0.05) and heart rate increased from 194 ± 10 to 227 ± 8 beats/min (p < 0.05; means ± SE). By 5 hr, blood pressure dropped to 67.5 ± 4 mm Hg and heart rate increased to 239 ± 8 beats/min. In piglets pretreated with 4-methylpyrazole, an alcohol dehydrogenase inhibitor, there was a transient increase in blood pressure (p < 0.05) and a decrease in heart rate (p < 0.05) immediately after the end of the ethanol infusion. However, the hemodynamic alterations observed 2 hr after ethanol treatment alone were prevented with 4-methylpyrazole. These findings indicate that ethanol metabolites play a significant role in hemodynamic alterations observed after acute ethanol intoxication. The mean ethanol metabolic rate derived from plasma data was 94 ± 9 mg/liter/hr. This corresponded to an apparent K m of 68 ± 3 mg/liter and a V m of 123 ± 11 mg/liter/hr. The V d was 0.966 ± 0.031 liter/kg. The metabolic rate for ethanol, derived from plasma data, correlated with in vitro alcohol dehydrogenase activity at pH 7.4 and 25 and 37°C. The optimum pH for hepatic alcohol dehydrogenase activity was 9.9.

Both acute and chronic exercise enhance in vivo ethanol clearance in rats.

Rates of ethanol clearance were measured at rest and with acute exercise in four groups of female Sprague-Dawley rats. Two groups were trained to run on a motor-driven rodent treadmill at 27 m/min, 1 h/day, 5 days/wk and were given a nutritionally balanced liquid diet; one of these groups received 35% calories as ethanol whereas in the other, sucrose was isocalorically substituted for the ethanol. Appropriate sedentary and nonethanol controls were also used. Clearance of a 1.75-g/kg ethanol dose injected intraperitoneally was determined by measuring ethanol levels in the blood each hour and utilizing these values in the Widmark equation (R. Teschke, F. Moreno, and A. Petrides, Biochem. Pharmacol. 30: 1745-1751, 1981) for calculating whole-body ethanol clearance. Rates of ethanol clearance were determined for each rat at 4 and 7 wk of training. The clearance tests at 4 wk included a 60-min period of running exercise, whereas the tests 3 wk later were conducted at rest. The results indicate that both acute exercise and exercise training can increase rates of in vivo ethanol clearance. In addition, the chronic exercise appeared to increase in vitro ethanol metabolism by hepatic microsomes without altering in vitro hepatic alcohol dehydrogenase activity.

The metabolism of acetaldehyde and not acetaldehyde itself is responsible for in vivo ethanol-induced lipid peroxidation in rats

A single oral administration of ethanol (5 g/kg) to rats induced a marked increase in lipid peroxidation, in the liver and kidney within 9 hr, as assessed by malondialdehyde accumulation. The pretreatment with alcohol dehydrogenase (ADH) inhibitor, 4-methylpyrazole (1mmol/kg) caused approximately 50% inhibition of the hepatic ADH activity and abolished this ethanol-induced lipid peroxidation. The disulfiram treatment (100mg/kg) significantly inhibited 63% of the hepatic low K m aldehyde dehydrogenase (ALDH) but not the high K m ALDH. The cyanamide treatment (15mg/kg) effectively decreased 83% of the low K m and 70% of the high K m ALDH in the liver. Although there was more than a 20-fold elevation of acetaldehyde levels by the inhibition of acetaldehyde metabolism with disulfiram or cyanamide, the ethanol-induced lipid peroxidation was significantly suppressed by pretreatment with these drugs. More than 90% inhibition of xanthine oxidase and dehydrogenase by the pretreatment with allopurinol (100 mg/kg), with no effect on the hepatic ADH and ALDH activities, did not alter the enhancement of lipid peroxidation following ethanol administration. We propose that the metabolism of acetaldehyde (probably via the low K m ALDH) and not acetaldehyde itself is responsible for the ethanol-induced lipid peroxidation in vivo and that the contribution of xanthine oxidase, as an initiator of lipid peroxidation through acetaldehyde oxidation is minute during acute intoxication.