Effect of Ukrain on human liver alcohol dehydrogenase activity in vitro

In the present study it was found that Ukrain inhibits the ethanol oxidation process catalyzed by human alcohol dehydrogenase (ADH). Ukrain at a concentration of 10(-6), 2.5 x 10(-6), and 5.0 x 10(-6) M decreased liver ADH activity in the presence ethanol (approximately 8.41%, 13.28%, 16.69%, respectively) as well as in the presence of methanol (approximately 13.29%, 19.07% and 42.20%, respectively).     

Effect of allyl alcohol on xanthine dehydrogenase activity in the perfused rat liver

Xanthine oxidase has been implicated in the production of reactive oxygen species and cell injury produced by various toxic compounds. Since allyl alcohol injuries the liver by an oxygen-dependent mechanism, we examined the actions of this hepatotoxicant on the conversion of xanthine dehydrogenase into xanthine oxidase in perfused livers. A microassay for NAD(+)-dependent xanthine dehydrogenase, based on measuring the production of NADH fluorometrically under anaerobic conditions, was developed and used to examine the actions of allyl alcohol on this activity in periportal and pericentral regions of the liver lobule. The oxygen-dependent activity, xanthine oxidase, was monitored in whole liver homogenates by uric acid formation at 302 nm under aerobic conditions. Perfusion of the liver with allyl alcohol (350 microM) increased xanthine oxidase and decreased xanthine dehydrogenase in whole liver consistent with the hypothesis that allyl alcohol enhanced calcium-dependent proteolytic conversion of the NAD(+)-dependent to the O2-dependent form. Xanthine dehydrogenase was higher in pericentral than in periportal regions of the liver lobule and tended to decrease selectively in periportal zones of livers exposed to allyl alcohol. O2 uptake was stimulated transiently by allyl alcohol followed by subsequent inhibition of respiration. These results are consistent with the idea that conversion of NAD(+)-dependent xanthine dehydrogenase to xanthine oxidase is involved in the zone-specific hepatotoxicity of allyl alcohol.     

The role of lys-228 residue in horse liver alcohol dehydrogenase activity

Archives of Pharmacal Research - Lys-228 in horse liver alcohol dehydrogenase isoenzyme E (HLADH-E) was mutated to glycineby site-directed mutagenesis. The specific activity of the mutant enzyme...     

Effects of castration and testosterone administration on rat liver alcohol dehydrogenase activity

The effects of castration and testosterone administration on the activity of liver alcohol dehydrogenase and on the rate of ethanol elimination were determined in male Sprague-Dawley rats. Castration increased liver alcohol dehydrogenase activity. The total liver activity in castrated animals was 2.37 ± 0.229 (S.E.) $\text{mmoles}\text{hr}$ as compared with a value of 1.39 ± 0.125 $\text{mmoles}\text{hr}$ in sham-operated controls (P < 0.01). Testosterone administration partially suppressed the enhanced activity of liver alcohol dehydrogenase produced by castration. By contrast, in control animals testosterone administration resulted in a small paradoxical increase in liver alcohol dehydrogenase. The increase in the enzyme activity in castrated animals was associated with a parallel increase in the rate of ethanol elimination. Castrated and control animals showed decreases in free cytosolic and mitochondrial NAD⁺/NADH ratios after ethanol administration. These observations suggest that testosterone (and probably other as yet unknown factors modified by castration) affects liver alcohol dehydrogenase activity, and that the total enzyme activity can be a principal limiting factor in ethanol elimination.     

Developmental changes in mouse liver alcohol dehydrogenase

Alcohol dehydrogenase activity in the supernatant fraction of liver homogenates was studied in adult and newborn mice. Newborn mice were found to have a lower specific activity than adult animals. K_m values were higher in the new born animal. Electrophoresis showed two bands for the adult and only one for the newborn, with a greater intensity seen in adult.     

Ontogeny of the activity of alcohol dehydrogenase and aldehyde dehydrogenases in the liver and placenta of the guinea pig

The objectives of this study were to elucidate the ontogeny of the activity of alcohol dehydrogenase (ADH), low Km aldehyde dehydrogenase (ALDH) and high Km ALDH in the liver and placenta of the guinea pig, and to determine the relationship between the relative activity of each enzyme in the guinea pig maternal-placental-fetal unit and the disposition of ethanol and its proximate metabolite, acetaldehyde. The enzyme activities were determined in maternal liver, fetal liver, and placenta of the guinea pig at 34, 50, 60 and 65 days of gestation (term, about 66 days), in the liver of the 2-day-old neonate, and in adult liver. There was low ADH activity in fetal liver and placenta throughout gestation and in neonatal liver. The fetal liver low Km ALDH activity increased progressively and, at 60 days of gestation, was similar to adult liver activity, as was also the case for neonatal liver enzyme activity. Placental low Km ALDH activity was less than adult liver activity throughout gestation. Fetal hepatic high Km ALDH activity increased during gestation, but was less than adult liver activity, as was also the case for neonatal liver enzyme activity. Placental high Km ALDH activity was low throughout gestation. For oral administration of 0.5 g ethanol/kg maternal body weight to pregnant guinea pigs at mid-gestation (34 days), the maternal blood and fetal body ethanol concentration-time curves were similar. Acetaldehyde was measurable in maternal blood and fetal body at similar concentrations, which were 100- to 1000-fold less than the respective ethanol concentrations. The major difference in the disposition of ethanol and acetaldehyde at near-term pregnancy, compared with mid-gestation, was the lack of measurable acetaldehyde in fetal blood. These results indicate that the guinea pig fetus throughout gestation has virtually no capacity to oxidize ethanol, and its duration of exposure to ethanol is regulated by maternal hepatic ADH-catalyzed biotransformation of ethanol. The fetus, however, appears to have increasing low Km ALDH-dependent capacity to oxidize ethanol-derived acetaldehyde during development, and would appear to be increasingly protected from exposure to acetaldehyde as gestation progresses.     

Role of alcohol dehydrogenase in the swift increase in alcohol metabolism (SIAM). Studies with deer mice deficient in alcohol dehydrogenase

Previous studies have shown that rates of ethanol metabolism increase markedly 2-4 hr after the administration of ethanol in rats and in four inbred strains of mice. This phenomenon, called the swift increase in alcohol metabolism (SIAM), also exists in humans. To determine whether alcohol dehydrogenase (ADH) is necessary for the SIAM response, we compared ethanol metabolism in two strains of the deer mouse, Peromyscus maniculatus. One strain lacks alcohol dehydrogenase (ADH-negative), whereas the other strain has normal ADH levels (ADH-positive). Rates of ethanol elimination were determined after a single intraperitoneal injection of ethanol at different doses (0.5 to 3.0 g/kg) and also after both strains were exposed to various levels of ethanol vapor for 4 hr. The ADH-positive strain exhibited up to a 72% increase in the rate of ethanol elimination after exposure to ethanol vapor compared to the ethanol-injected controls. In contrast, treatment with ethanol vapor did not alter rates of ethanol elimination in the ADH-negative strain. These data demonstrate clearly that ADH is required for SIAM in the deer mouse. In addition, in both the ADH-positive and the ADH-negative strain, rates of ethanol elimination increased in both the ethanol-injected and vapor-treated groups 2- to 3-fold as the dose of ethanol was increased from 100 to 500 mg/100 ml. Thus, it is concluded that this "concentration effect" of ethanol on rates of ethanol metabolism does not involve ADH in the . deer mouse.     

Pyrazole-insensitive alcohol dehydrogenase activity in human serum

Serum alcohol dehydrogenase (ADH) activity in some individuals contains a fraction that is not inhibited by pyrazole. This might be due to the presence in those sera of π-ADH, a unique isoenzyme found recently in human liver, and which, according to one hypothesis, could be co-responsible for the development of alcohol dependence.     

Non-competitive inhibition of the alcohol dehydrogenase activity in rat liver by latamoxef, cefamandole or cefoperazone

High concentrations of 1 or 10 mmol/l latamoxef (LMOX), cefamandole (CMD) or cefoperazone (CPZ) in vitro non-competitively inhibit to a small extent the alcohol dehydrogenase isolated from rat liver in the presence of ethanol as a substrate, as is shown by enzyme-kinetic data evaluated in a Lineweaver-Burk diagram. This observation may serve as an approach to partially explain a possible delay of ethanol elimination from the blood after pretreatment with these beta-lactam antibiotics.     

The effect of structural analogs of triiodo-3,5,3'-L-thyronine on the activity of glutamate dehydrogenase and isocitrate dehydrogenase of liver and cardiac mitochondria and liver alcohol dehydrogenase in vivo and in vitro]

In thyroidectomized rats, 3,5,3'-triiodo-thyroformic (TF₃), 3,5,3'-triiodo-thyroacetic (TA₃) and 3,5.3'-triiodo-thyropropionic (TP₃) acids, which are structural analogs of 3,5,3'-triiodo-L-thyronine (LT₃), counteract the decrease of mitochondrial glutamate dehydrogenase (GlDH) activity and the increase of mitochondrial isocitrate dehydrogenase (ICDH) and cytoplasmic alcohol dehydrogenase (ADH) activities in liver. The effect of TA₃ is similar to that of LT₃, those of TP₃ and TF₃ being, in this order, lower. TF₃, TA, and TP3 have no effect on heart mitochondrial ICDH activity, an activity which does not appear to be influenced by thyroidectomy. In vitro, TF₃, TA₃ and TP₃ inhibit GlDH, ICDH and ADH activities when tested either on liver subcellular fractions or on pure enzymes: the effects are more pronounced on GlDH than on ADH or on ICDH. The three iodinated derivatives present differences in the competitive character of the inhibition they exert against the substrate or cosubstrate involved in the differeet enzyme reactions investigated.     

Sex-dependent induction of alcohol dehydrogenase activity in rats

The glycolethers 2-methoxyethanol (2-ME), 2-ethoxyethanol (2-EE), and 2-butoxyethanol are widely used organic solvents with teratogenic, spermatotoxic, and hematotoxic effects due to the respective alkoxyacetic acid metabolites formed via alcohol dehydrogenase (ADH). ADH displays sexually dimorphic activities in adult rats, and is probably at least in part under the control of testosterone. The aim of this study was to investigate whether induction of ADH is also sex-dependent. Ethanol, 2-ME, and 2-EE were tested as inducers of hepatic and gastric ADH in female, male, and castrated male rats. The activity of hepatic ADH was higher in female than in male rats, while the activity of gastric ADH was higher in male than in female rats. The activities of ADH increased with increasing chain length of the glycolethers and alcohols. Castration of male rats led to a female pattern of ADH activity, i.e. increased activity of hepatic ADH and decreased activity of gastric ADH. Ethanol had no inducing effect on hepatic ADH in either male or female rats. 2-ME and 2-EE caused an increase in the activity of hepatic ADH in male and castrated male rats only. The present data demonstrate a different expression of ADH isoenzymes in male and female rats, and a sex-dependent induction of ADH isoenzymes. The different possible regulatory mechanisms for the different ADH isoenzymes require further investigation.     

Human skeletal muscle lactate dehydrogenase activity in the presence of some alcohol dehydrogenase inhibitors

Methanol, ethylene glycol and other alcohol intoxications are complicated by severe acidosis which could be caused by formation of metabolic acids and additionally lactic acid production. An increasing nicotinamide adenine dinucleotide reduced/nicotinamide adenine dinucleotide oxidized (NADH/NAD) ratio during alcohol biotransformation is responsible for the induction of lactic acidosis. The main purpose of the present paper was to evaluate the effect of 4-methylpyrazole, cimetidine, ethylenediaminetetraacetic acid disodium salt, ethanol and methanol on lactate dehydrogenase (E.C. 1.1.1.27) activity and to discuss this issue. The activity of the enzyme was determined spectrophotometrically, in vitro using human enzyme skeletal muscle homogenates. 4-Methylpyrazole, cimetidine and ethylenediaminetetraacetic acid disodium salt at concentrations 0.01, 0.1, 1.0 mM and 12.5, 25.0, 50.0 mM of ethanol and methanol were studied. Our results showed that cimetidine increased lactate dehydrogenase activity as compared to the control at all tested concentrations. Such activity was noted for 4-methylpyrazole at 0.1 mM and higher concentration. By contrast, no significant effect on lactate dehydrogenase activity in the presence of ethylenediaminetetraacetic acid disodium salt, methanol and ethanol was observed.     

Effect of castration on the turnover of rat liver alcohol dehydrogenase

Castration increased liver alcohol dehydrogenase activity and enzyme protein in male rats. The turnover of alcohol dehydrogenase determined from the decline in radioactivity present in immunoprecipitated enzyme after injection of NaH¹⁴CO₃ was decreased after castration. The fractional rate of degradation (K_d) for the enzyme was 0.11 · day⁻¹ in the castrated as compared with 0.13 · day⁻¹ in the control animals (P < 0.05). The fractional rate of synthesis (K_s) of the enzyme was not affected by castration, while the absolute rate of synthesis was increased slightly. This study shows that a decrease in the rate of degradation is the principal cause for the increase in liver alcohol dehydrogenase following castration.     

The binding of sulfonamides to horse liver alcohol dehydrogenase

The binding of sulfonamides to the active site of horse liver alcohol dehydrogenase has been studied by their effect on affinity labelling and steady state kinetics. Affinity labelling with iodoacetate and BIP has been used to study binding to free enzyme. The unsubstituted sulfonamide, sulfanilamide (I), shows very weak binding compared to the other sulfonamides tested. Most important for binding is the type of substituent attached to the parent sulfonamide, particularly when as in sulfathiazole this is a heterocycle which binds to the catalytic zinc atom of the enzyme. For sulfathiazole the dissociation constant from the enzyme is pH dependent showing two pK_a values. The lower at pH 7 is the pK_a of the drug itself, while that at pH 9 agrees with the ionization of water bound to the catalytic zinc ion.Steady state kinetics have been carried out at pH 7.0 and 10.0 to examine sulfonamide binding to the enzyme when coenzyme is attached. Both NAD⁺ and NADH induce substrate competitive sulfonamide binding. Likewise sulfathiazole accelerates the dissociation of NADH from the enzyme and so V_max for alcohol oxidation. The latter like stimulation of the affinity labelling reaction with iodoacetate is considered to result from binding of the thiazole ring to the catalytic zinc ion. With all the sulfonamides examined hydrophobic binding and charge are important in determining affinity to the active site and the mode of binding. Sulfonamides containing pyrazole or imidazole rings can be important in alcohol therapy.     

Viability of cells in ethanol. Role of alcohol dehydrogenase.

Rodent cells were found to contain a high level of alcohol dehydrogenase activity which was not inducible. Other hepatoma and nonhepatoma cell lines were tested and found to contain lower but measurable levels of alcohol dehydrogenase.