Hepatic Aldehyde Dehydrogenase Activity Research Articles

6-(Methylsulfinyl)hexyl isothiocyanate protects acetaldehyde-caused cytotoxicity through the induction of aldehyde dehydrogenase in hepatocytes

In the body, alcohol dehydrogenase rapidly converts ethanol to its toxic metabolite, acetaldehyde, which is further metabolized to non-toxic acetic acid by aldehyde dehydrogenase (ALDH). 6-(methylsulfinyl)hexyl isothiocyanate (6-MSITC), a major bioactive compound in Wasabi (Wasabia japonica) has various physiological effects such as anti-oxidative, anti-inflammatory and anti-cancer effects. However, the effect of 6-MSITC on alcohol metabolism has not been studied. In this study, we investigated the effects of 6-MSITC on hepatic ALDH activity and protein expression both in vitro and in vivo. 6-MSITC inhibited ethanol- and acetaldehyde-induced cytotoxicity. Treatment with 6-MSITC to HepG2 cells enhanced ALDH activity through the induction of mitochondrial ALDH2 expression, but not cytosolic ALDH1A1. Knockdown of Nrf2 canceled the 6-MSITC-induced ALDH2 expression, indicating that Nrf2 regulated ALDH2 expression. Moreover, 6-MSITC increased the nuclear translocation of Nrf2 and the expression levels of HO-1 and SOD2, Nrf2-regulated phase II drug-metabolizing enzymes. Oral administration of 6-MSITC increased the mitochondrial ALDH2 activity and its expression in the liver of C57BL/6J mice. These results suggested that 6-MSITC is possible to protect acetaldehyde toxicity in hepatocytes by induction of mitochondrial ALDH2 expression through Nrf2/ARE pathway.

오이를 이용한 기능성 식초 음료 개발

This study was performed to develop functional vinegar by using cucumbers through two stages of fermentation. The alcohol content was maximized (7.8%) after 6-days of alcohol fermentation at 25℃ by adjusting the initial sugar concentration to 15°Brix, and vinegar with an acidity of 5.8% was obtained after 12-days of acetic acid fermentation at 30℃. The major sugars in the produced vinegar were glucose and fructose, which were present in concentrations of 3,067.26 and 395.73 ㎎%, respectively. The major organic acids were acetic acid and succinic acid, which were present in concentrations of 4,410.5 and 841.11 ㎎%, respectively. The total free amino acid content of the cucumber vinegar was 181.45 ㎍/㎖ and citrulline, valine, aspartic acid, asparagine, and ornithine were the major amino acids. The inorganic components included various alkaline elements, such as K, Ca, and Mg. In addition, experimental methods to assess the DPPH and ABTS? radical-scavenging ability, reducing power, and β-carotene bleaching activity showed that the cucumber vinegar had strong antioxidant properties. The total polyphenol content, which are the major components responsible for the antioxidant activities of the cucumber vinegar, was 40.14 ㎎/100 ㎖. The cucumber vinegar showed significantly higher hepatic aldehyde dehydrogenase activity when compared to the alcoholic control (negative) and the marketing drink (positive), resulting in decreased plasma acetaldehyde concentrations in rats. These results demonstrate that cucumber vinegar possesses antioxidant properties and holds great promise for use in preventing hangovers.

오이 발효음료가 만성적으로 에탄올을 급여한 흰쥐의 에탄올 대사와 항산화방어계에 미치는 영향

Cucumber fermentation has been used as a means of preservation. This study was performed to investigate the effects of fermented cucumber beverage (CF) containing beneficial materials for an ethanol hangover based on Hovenia dulcis (SKM) on ethanol-induced hepatotoxicity. Male Sprague-Dawley rats were randomly divided into three groups: ethanol control, ethanol plus SKM, and ethanol plus CF+SKM. SKM or CF+SKM was orally administered at a dose of 7 mL/kg body weight once per day for 5 weeks. Control rats were given an equal amount of water. CF+SKM significantly lowered plasma ethanol levels, whereas SKM tended to decrease the levels compared to the control. Both SKM and CF+SKM significantly lowered the plasma acetaldehyde levels and serum transaminase activities compared to those in the control. SKM and CF+SKM did not affect hepatic alcohol dehydrogenase activity; however, it significantly inhibited cytochrome P450 2E1 (CYP2E1) activity. Hepatic aldehyde dehydrogenase (ALDH) activity was significantly higher in the SKM and CF+SKM groups than that in the control group. Plasma acetaldehyde concentration was significantly correlated with hepatic CYP2E1 (r

Priming dose of phenylhydrazine protects against hemolytic and lethal effects of 2-butoxyethanol

Protection against a high dose of a toxicant by prior exposure to another toxicant is called heteroprotection. Our objective was to establish a heteroprotection model in RBCs. Female Sprague Dawley rats treated with an LD90 dose of 2-butoxyethanol (BE, 1500 mg/kg in water, 5 ml/kg po) 14 days after priming with 0.9% NaCl suffered 90% mortality by 15 days, whereas all rats receiving the LD90 dose of BE 14 days after priming with phenylhydrazine (PHZ, 125 mg/kg in 0.9% NaCl, 3 ml/kg po) survived. Hematocrit decreased from normal 45% to 24% by day 3 after PHZ priming and improved thereafter. Increasing the time interval between the priming and LD90 dose to 21 days abolished the heteroprotection. RBCs obtained on days 7 and 14 after PHZ priming unlike those on day 21 were resilient to the hemotoxic metabolite of BE, butoxyacetic acid (BAA). Unaltered hepatic alcohol and aldehyde dehydrogenase activities upon PHZ priming suggested that bioactivation of BE to BAA was unaffected. Lower renal (6 and 12 h) and hepatic (12 h) BAA levels and 3 fold higher excretion of BAA in PHZ-primed rat urine suggested a protective role of toxicokinetics. Higher erythropoietin, reticulocytes, and resiliency of PHZ-primed rat RBCs indicated that newly formed RBCs are resilient to hemolytic BAA. The antioxidant levels in the PHZ-primed rat RBCs did not indicate a protective role in heteroprotection. In conclusion, the resistance of PHZ-primed rats against BE-induced hemotoxicity and lethality is mediated by a combination of altered toxicokinetics, robust erythropoiesis, and resiliency of new RBCs.

The effects of pregnancy on ethanol clearance

We have studied the effects of pregnancy on ethanol clearance rates and on blood and urine ethanol concentrations (BECs and UECs) in adult Sprague–Dawley rats infused with ethanol intragastrically. Pregnant rats had greater ethanol clearance following an intragastric or intravenous ethanol bolus (3 or 0.75 g/kg, respectively) relative to non-pregnant rats ( p < 0.05). Pregnant rats infused with ethanol-containing diets for several days had lower ( p < 0.05) UECs than non-pregnant rats when given the same dose of ethanol. Non-pregnant rats infused ethanol-containing diets at two levels of calories (the higher caloric intake required by pregnant rats [220 kca/kg 75/d] or the normal calories required for non-pregnant rats [187 kcal/kg 75/d]) had statistically equal UECs, suggesting that increased caloric intake was not responsible for the effect of pregnancy. While the activity of hepatic alcohol dehydrogenase (ADH) did not differ with pregnancy, gastric ADH activity was increased ( p < 0.001). Furthermore, total hepatic aldehyde dehydrogenase (ALDH) and hepatic mitrochrondrial protein were increased ( p < 0.05) and hepatic CYP2E1 activity was suppressed ( p < 0.05). The results suggest that pregnancy increases ethanol elimination in pregnant rats by: 1) induction of gastric ADH; 2) elevated hepatic ALDH activity; and 3) increased mitochondrial respiration. The greater ethanol clearance results in lower tissue ethanol concentrations achieved during pregnancy for a given dose, and this may have clinical significance as a mechanism to protect the growing fetus from ethanol toxicity.

Biochemical effects of chloral hydrate on male rats following 7-day drinking water exposure.

The biochemical and toxicological effects of chloral hydrate were investigated. Four groups (n = 7 per group) of male Sprague-Dawley rats (161-170 g) were administered chloral hydrate in drinking water at concentrations of 20, 200 or 2000 ppm for 7 days. The control group received phosphate-buffered water only. There were no treatment-related changes in the body weight gains, relative weights of major organs or haematological parameters. Trichloroacetic acid was significantly (P < 0.05) elevated in the serum of high-dose animals (7.75 +/- 5.14 mg dl(-1), mean +/- SD). In the high-dose animals there was a 36% increase in protein level in the liver homogenates but not in the corresponding 9000 g supernatants. Concurrently, there was a threefold increase in the activity of the hepatic peroxisomal enzyme palmitoyl CoA oxidase (PCO). A prominent change was the dose-related suppression in hepatic aldehyde dehydrogenase (ALDH) activity observed in all treatment groups, with the decrease ranging from 15% at 20 ppm to 68% at 2000 ppm. There were no significant decreases in the activity of hepatic enzymes ethoxyresorufin O-deethylase (EROD), benzyloxyresorufin O-dealkylase (BROD) and UDP-glucuronosyl-transferase (UDPGT). In the high-dose group there was a 30% increase in hepatic glutathione-S transferase (GST) activity, accompanied by a 13% increase in glutathione (GSH). Significant effects on lipids were observed in the liver of the high-dose animals, with a 15% decrease in hepatic cholesterol and triglyceride levels. There were no treatment-related changes in serum chemistry parameters, including cholesterol and triglyceride levels. Although in vitro assays showed chloral hydrate to be an inhibitor of serum pseudocholinesterase activity, with a 50% inhibition concentration (ic(50)( of approximately 0.7 mM at 5 mM butyrylthiocholine, no decrease in serum pseudocholinesterase activity was found in the treated animals. It was concluded that the liver is the target organ for chloral hydrate, with suppression of ALDH as the most sensitive endpoint followed by alteration in the GSH level and GST activity. Changes observed in the high-dose animals, such as increased peroxisomal PCO activity in the liver and perturbation of lipid homeostasis in the liver and blood, were likely to be associated with trichloracetic acid, the major metabolite of chloral hydrate.

Influence of chronic alcohol abuse and liver disease on hepatic aldehyde dehydrogenase activity

Alcohol metabolism results in the production of acetaldehyde, a compound that is much more toxic than ethanol itself. Hepatic aldehyde dehydrogenase (ALDH) is the main enzymatic system responsible for acetaldehyde clearance from the hepatocyte. The objective of this study was to determine the modifications in ALDH activity due to chronic alcohol abuse and liver disease. ALDH activity was determined in samples of liver tissue from 69 alcoholic and 82 nonalcoholic subjects, with and without liver disease. According to the results of liver pathology examination, alcoholic patients were classified into the following groups: controls, with no liver disease (group 1), noncirrhotic liver disease patients (group 2), and cirrhotics (group 3). Nonalcoholic subjects were categorized, using the same criteria, into groups 4, 5, and 6, respectively. ALDH activity was determined spectrophotometrically at two substrate concentrations: 18 mM for total activity and 180 μM for low K m activity. High K m activity was calculated by subtracting the low K m activity value from that of total ALDH activity. Results obtained in each group were expressed as the mean ± SD of mU of g of wet weight. There were no significant differences when the total ALDH activity from the alcoholic and the nonalcoholic patients with a similar degree of liver pathology were compared: group 1, 1257 ± 587 vs. group 4, 1328.1 ± 546.2 ( p: NS); group 2, 919.1 ± 452.4 vs. group 5, 753.5 ± 412 ( p: NS); and group 3, 430.2 ± 162.4 vs. group 6, 473.2 ± 225.3 ( p: NS). On the other hand, total ALDH activity was significantly lower in cirrhotics than in controls, both among alcoholics ( p < 0.01) and among nondrinkers ( p < 0.05). The low K m activity was severely reduced in cirrhotics, both alcoholics and nonalcoholics ( p < 0.01). High K m activities in cirrhotic patients were low, compared to controls, both in alcoholics and nonalcoholics, although the difference was nonsignificant. The results of the present study suggests that chronic alcohol abuse does not depress ALDH activity. A reduction in the ALDH activity detected in patients with severe liver disease (cirrhotics) was clearly a consequence of liver damage. This reduction was due mainly to a decrease of the low K m ALDH activity, but a trend to a decrease in the high K m ALDH activity was also detected.

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.

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)

Inducibility of liver cytosolic aldehyde dehydrogenase activity in various animal species

1. The inducibility of hepatic cytosolic aldehyde dehydrogenase activity was studied in rat, mouse, guinea pig, chicken, frog, salamander and rainbow trout, by using two different types of inducers of drug metabolism. 2. Phenobarbital (a type I inducer of drug metabolizing enzymes) increased total liver cytosolic aldehyde dehydrogenase activity (up to 20-fold) in a genetically defined substrain of responsive rats (RR) and only slightly, if at all, in a non-responsive substrain (rr). On the contrary, both types of rats showed a highly induced aldehyde dehydrogenase activity after treatment with methylcholanthrene (a type II inducer). Phenobarbital is affecting mainly an isozyme of aldehyde dehydrogenase, which is best measured with propionaldehyde as the substrate and NAD as the coenzyme (P/NAD). 3. Administration of phenobarbital to mice produced only a slight increase (2-fold) in the P/NAD aldehyde dehydrogenase activity. 4. Methylcholanthrene treatment caused a 2-fold increase of the hepatic P/NAD aldehyde dehydrogenase activity in the chicken. 5. In the guinea pig, phenobarbital produced an approximate 3-fold increase of the P/NAD activity. Methylcholanthrene had a similar effect, although to a lesser extent. 6. In the salamander, a 4-fold increase was detected in the enzyme activity measured with benzaldehyde as the substrate and NADP as the coenzyme (B/NADP), after treatment with either phenobarbital or methylcholanthrene. 7. The hepatic aldehyde dehydrogenase activities were found unchanged in the rainbow trout, after treatment with phenobarbital or 2,3,7,8-tetrachlorodibenzo- p-dioxin. 8. The rat model remains the only one examined that shares with human hepatocytes strong inducibility of the B/NADP aldehyde dehydrogenase isozyme upon treatment with polycyclic aromatic hydrocarbons.

Tissue distribution of inducible aldehyde dehydrogenase activity in the rat after treatment with phenobarbital or methylcholanthrene.

Two genetically distinct substrains of the Wistar rat (RR and rr) were used to study the tissue distribution of the inducibility of aldehyde dehydrogenase (ALDH). The RR substrain is responsive to phenobarbital (PB), as far as the induction of the hepatic ALDH activity is concerned, whereas the rr substrain is deprived of this biochemical property. Both substrains, however, respond to treatment with methylcholanthrene (MC), exhibiting a uniform increase of the ALDH activity in the liver. It is known that PB and MC induce two different isozymes of the hepatic cytosol. The effect of PB (1 g/l in drinking water, for 12 days) on the inducibility of ALDH in extrahepatic tissues was examined in the RR substrain. On the contrary, MC was given (50 mg/kg x 4, intraperitoneally) to rr animals. The activity of ALDH was found to be induced by PB in the liver and the intestinal mucosa, when measured with NAD and propionaldehyde (P/NAD) or phenylacetaldehyde (Ph/NAD). An increase of the activity was also noticed when ALDH was measured with NADP and benzaldehyde (B/NADP). In rr animals, MC induced the B/NADP activity in the liver, the intestinal mucosa, the kidneys, the lungs, the spleen, the brain, the urinary bladder and the heart. The effect of MC on various tissues was less distinct, when ALDH was measured as P/NAD or Ph/NAD activity. It is concluded, that PB and MC not only induce different types of ALDH activity, but they also reveal differences in the tissue distribution of the inducibility of ALDH.

Effect of disulfiram on canine liver aldehyde dehydrogenase activity: in vivo inactivation in a nonrodent animal model.

Dogs were used as nonrodent animal models to study the in vivo effects of disulfiram on hepatic aldehyde dehydrogenase (ALDH) activity. Dogs were treated with disulfiram either intraperitoneally or orally (100 mg/kg/day for 2 days followed by 40 mg/kg/day for 3 days). Liver biopsies from control and treated animals were fractionated by differential centrifugation and the subcellular fractions were analyzed for ALDH activity. Significantly less activity was observed in cell homogenates from treated animals (20-50% of control activity per gram of liver). The majority of loss in activity was accounted for by a decrease in ALDH activity in the soluble fraction of the cell (12-30% of control activity) and in the mitochondrial fraction (23-30% of control activity). Activities at both high (5 mM) and low (50 microM) acetaldehyde concentrations were affected. The subcellular distribution of ALDH activity and in vivo inhibition by disulfiram in dogs is different from that reported for rats.

Erythrocyte aldehyde dehydrogenase activity in alcoholic subjects and its value as a marker for hepatic aldehyde dehydrogenase in subjects with and without liver disease.

Erythrocyte aldehyde dehydrogenase activity was assayed in actively drinking alcoholics, patients with alcoholic liver disease who claimed to be abstaining, patients with non-alcoholic liver disorders and normal controls. Hepatic cytosolic aldehyde dehydrogenase was also assayed in the majority of the subjects. Actively drinking alcoholics had significantly lower erythrocyte aldehyde dehydrogenase activity than controls (P less than 0.01) but abstaining alcoholic liver disease and non-alcoholic liver disorder subjects did not. There was a significant correlation between erythrocyte and hepatic cytosolic aldehyde dehydrogenase activity in the control group (r = 0.94, P less than 0.05) but not in the other study groups.

EFFECTS OF DIETS DECREASING ETHANOL CONSUMPTION ON ACETALDEHYDE METABOLISM IN UChA AND UChB RATS

It has previously been reported that the introduction of a new issue (D1) of a stock diet (D0) caused a significant decrease in voluntary ethanol consumption in rats of our UChA (low ethanol consumer) and UChB (high ethanol consumer) strains, and that, after changing to a diet lacking in animal products (D3), ethanol consumption reached the previous level attained in UChB rats and exhibited a bimodal distribution in UChA rats in such a way that about one-third of these consumed more than 2 ml of a 10% (v/v) ethanol solution per 100 g of body weight, as did UChB rats. When UChA rats exhibiting high ethanol consumption and also UChB rats were fed on the D3 diet with a brewer's yeast supplement, a significant decrease in ethanol intake was observed. Since significant correlations of voluntary ethanol intake to blood acetaldehyde levels, and to hepatic and brain aldehyde dehydrogenase (AldDH) activities, have been reported, the effects on these parameters of diet D1 and of supplements of brewer's yeast or disulfiram were studied. Results showed that rats of both strains fed on a D1 diet exhibited a significant increase in blood acetaldehyde level after ethanol administration, concomitant with an inhibition of hepatic and brain AldDH activities and a significant decrease in ethanol intake. Thus, this effect could be related to a disulfiram-like activity. The decrease in ethanol intake induced by brewer's yeast was not accompanied by changes of blood acetaldehyde level after ethanol, nor by inhibition of hepatic AldDH activity in either strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehyde dehydrogenase in alcoholic subjects.

Hepatic aldehyde dehydrogenase activity is depressed in alcoholic liver disease and may account for the observation that alcoholics develop high blood acetaldehyde concentrations following ethanol. To determine whether this is a specific defect in alcoholics, aldehyde dehydrogenase was studied in liver tissue obtained from three groups of subjects. Group I comprised 30 patients with alcoholic liver disease, Group II consisted of eight subjects with liver disease unrelated to alcohol abuse and Group III was a control group of 10 individuals with no significant liver disease. Mean hepatic aldehyde dehydrogenase activity was significantly lower in Group I than in Groups II or III [4.9 +/- 0.6 (mean +/- S.E.), compared to 10.2 +/- 1.8 and 12.4 +/- 1.1 nmoles of acetaldehyde oxidized per min X mg of protein, respectively]. Aldehyde dehydrogenase activity in Group II was relatively well maintained. Aldehyde dehydrogenase activity was found in cytosolic and mitochondrial fractions of liver homogenates. In alcoholic subjects, cytosolic aldehyde dehydrogenase activity was not more depressed than was mitochondrial aldehyde dehydrogenase. Isoelectric focusing demonstrated a single mitochondrial isoenzyme and a single cytosolic isoenzyme in most cases in Group III. In contrast, multiple cytosolic isoenzymes were consistently found in liver tissue from Group I subjects. These findings suggest that depressed aldehyde dehydrogenase activity in alcoholic subjects is not a consequence of liver disease.

Ethanol feeding can produce secondary alterations in aldehyde dehydrogenase isozymes

Depressed hepatic aldehyde dehydrogenase (ALDH) activity levels have been observed in alcoholics, but whether the deficit is primary or secondary in nature remains controversial. In this study, we examined liver ALDH in rodent (rat) and primate (baboon) animal models pair-fed nutritionally adequate ethanol or isocaloric carbohydrate containing liquid diets. Both species show qualitative changes in ALDH isozymes after ethanol consumption. The changes include alterations in isozyme patterns seen upon electrofocusing and decreased responsiveness to the ALDH inhibitor, disulfiram. The subcellular locus of most of the changes is cytosolic in the baboon and mitochondrial in the rat. Study of partially purified (enriched) baboon cytosolic ALDH confirmed changes seen in the original cytosols and kinetic characterization of the enriched enzyme revealed a 9-fold higher K m for acetaldehyde in ALDH from an ethanol treated animal. We note that qualitative and quantitative changes secondary to ethanol treatment in the primate model closely parallel those described in human alcoholics.

Comparative subcellular distribution of aldehyde dehydrogenase in rat, mouse and rabbit liver

The subcellular distribution of hepatic aldehyde dehydrogenase (ALDH) activity was determined in Buffalo, Fischer 344, Long-Evans, Sprague-Dawley, Wistar and Purdue/Wistar rats. These subcellular distributions were compared to the distribution of mouse and rabbit liver ALDH. For the six rat strains, at millimolar propionaldehyde concentrations, NAD-dependent ALDH activity was associated primarily with mitochondria (51%) and microsomes (30%). At millimolar acetaldehyde concentrations, NAD-dependent ALDH was primarily mitochondrial (up to 80%). Less than 1% of total NAD-dependent aldehyde dehydrogenase was found in the cytosol. The highly inbred Purdue/ Wistar line possessed significantly less acetaldehyde-NAD ALDH activity as well as less total NADP-dependent ALDH activity than the other strains. In CD-1 mouse liver, millimolar K m NAD-dependent ALDH activity was found in mitochondria (60%), microsomes (23%) and cytosol (5%). In rabbit liver, millimolar K m NAD-dependent ALDH was also distributed among mitochondria (36%), microsomes (19%) and cytosol (28%). At micromolar substrate concentrations, mitochondria possessed the majority of rat, mouse and rabbit liver ALDH activity. In all three species, NADP-dependent ALDH activity was found predominantly in the microsomal fraction (up to 65%). The cytosol possessed little NADP-dependent ALDH in any species. We conclude that there are significant species differences in the subcellular distribution of aldehyde dehydrogenase between rat, mouse and rabbit liver. In all three species, mitochondria and microsomes possessed the majority of hepatic aldehyde dehydrogenase activity. However, the cytosol of mouse and rabbit liver also made a significant contribution to total ALDH activity. For the six rat strains examined, liver cytosol possessed little or no ALDH activity.

EFFECT OF ALCOHOL CONSUMPTION ON HEPATIC ALDEHYDE DEHYDROGENASE ACTIVITY IN ALCOHOLIC PATIENTS

Two liver biopsies were performed 6 months apart in each of 29 patients with alcoholic liver disease. Hepatic aldehyde dehydrogenase activity was measured on each occasion. The patients were seen regularly and their alcohol consumption was assessed independently. Hepatic aldehyde dehydrogenase activity was unchanged in 17 patients who continued to drink to excess; it rose in 10 patients who significantly reduced their alcohol intake; and it fell dramatically in 2 patients who were virtually abstinent initially, but then began drinking heavily. These results clearly demonstrate that alcohol consumption itself depresses hepatic aldehyde dehydrogenase activity. It is unlikely that the low hepatic aldehyde dehydrogenase activity reported in alcoholics represents a primary abnormality predisposing to alcoholism or alcoholic liver disease.

Decrease in calcium carbimide (calcium cyanamide)-induced inhibition of rat hepatic aldehyde dehydrogenases by multiple ethanol administration.

Ethanol (0.3 g/kg) was administered intravenously to adult, male rats at 3 h or at 1 and 3 h after gastric intubation of 7 mg/kg calcium carbimide (CC). For animals administered CC and two ethanol doses, blood ethanol concentration was similar for the two doses; however, blood acetaldehyde concentration was significantly less for the second ethanol dose compared with the first dose as determined by the area-under-curve data. Hepatic aldehyde dehydrogenase activity was determined over the 3.5- to 5-h interval after CC pretreatment. The inhibition of low Km and high Km aldehyde dehydrogenase activity in liver homogenate and in hepatic mitochondrial, cytosolic, and microsomal fractions was significantly less for rats administered CC followed by two ethanol doses compared with that for animals administered CC alone or CC followed by one ethanol dose. The data demonstrate that increased acetaldehyde concentration, produced during the CC - ethanol interaction, can augment the recovery of hepatic aldehyde dehydrogenase activity following CC pretreatment and indicate the existence of a displaceable enzyme inhibitor derived from CC.