The effect of ethanol administration on renal and hepatic mixed-function oxidases in the Fischer 344 rat

Alcohol induced effects on kidney

After administration ethanol and its metabolites go through kidneys and are excreted into urine, and its content in the urine is higher than that of the blood and the liver. Chronic ethanol administration decreases the renal tubular reabsorption and reduces renal function. Multiple functional abnormalities of renal tubules may be associated with ethanol-induced changes in membrane composition and lipid peroxidation. The vulnerability of the kidney to oxidative damage has been partly attributed to its high content of long-chain polyunsaturated fatty acids. Renal ultra structural abnormalities due to ethanol exposure may be important in the genesis of functional disturbances. Increased oxidative stress and endothelial dysfunction with their complex interrelationships are relevant aspects of atherogenesis in chronic renal failure. Antioxidants, particularly polyphenols are expected to decrease the vulnerability of the kidney to oxidative challenges.

Characterization of the cytochrome P-450 monooxygenase system of hamster liver microsomes. Effects of prior treatment with ethanol and other xenobiotics

The cytochrome P-450 monooxygenase system of hamster liver microsomes and its response to prior treatment with ethanol and other xenobiotics have been examined. Male Syrian golden hamsters were administered ethanol (ETOH), phenobarbital (PB), 5,6-benzoflavone (BF) or isoniazid (INH). Each treatment resulted in a moderate increase (20-60%) in the specific content of liver microsomal cytochrome P-450 along with a unique hemeprotein ferrous carbonyl Soret maximum. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of liver microsomes revealed distinctive changes in protein banding patterns in the cytochrome P-450 (45-60 kDa) region with each treatment. NADPH: cytochrome c reductase activity was increased by both PB and INH, whereas cytochrome b5 content was increased by INH only. Microsomal oxidation of ETOH and aniline p-hydroxylation (expressed per nmol cytochrome P-450) were enhanced dramatically by ETOH and INH, whereas PB and BF had no effect on these enzymatic activities. Both ETOH and INH also increased zoxazolamine 6-hydroxylation but, in contrast to other rodent species, this drug-metabolizing activity was decreased in hamster liver microsomes after treatment with either PB or BF. Microsomal benzphetamine N-demethylation was decreased by ETOH, INH and BF administration and was only modestly enhanced after treatment with PB. ETOH and INH had no effect on the O-deethylation of 7-ethoxycoumarin, and enzymatic activity increased by BF but decreased by PB. These results demonstrate that the cytochrome P-450-dependent monooxygenase system of hamster liver microsomes responds to treatment with ETOH and other xenobiotics in a manner that is quantitatively and, in certain respects, qualitatively different from that reported for the rat, rabbit, and mouse.

Differential effect of chronic ethanol consumption by the rat on microsomal oxidation of hepatocarcinogens and their activation to mutagens

The effect of chronic ethanol consumption by rats on hepatic microsomal activation of the hepatocarcinogens dimethylnitrosamine (DMN) and 2-acetylaminofluorene (2-AAF) was investigated. There was a marked increase in the rate of the oxidative demethylation of DMN and its activation to a mutagen by microsomes following ethanol intake. N- and C-hydroxylation of 2-AAF were measured at substrate concentrations ranging from 2 to 70 microM. The ratio of formation of N-hydroxy-2-acetylaminofluorene to C-hydroxy-2-acetylaminofluorenes increased with decreasing substrate concentration, suggesting enhanced carcinogenic potential of 2-AAF with diminishing levels of carcinogen. Kinetic analysis indicated that N-hydroxylation as well as 7-, 5- and 3-hydroxylation of 2-AAF do not follow Michaelis-Menten kinetics. In contrast to the marked inductive effect of ethanol consumption on the metabolic activation of DMN, only a minimal random effect on the N-hydroxylation of 2-AAF was demonstrable in two separate experiments. Furthermore, N-hydroxylation of 2-AAF by microsomes from control and ethanol-treated rats followed similar kinetics. While ethanol consumption enhanced the mutagenic activation of DMN by hepatic microsomes, no such effect of ethanol consumption on the conversion of 2-AAF to a mutagen was observed. The data indicate that chronic ethanol consumption does not have a general inductive effect on the microsomal activation of hepatocarcinogens.

Studies on the mechanisms of induction of N-nitrosodimethylamine demethylase by fasting, acetone, and ethanol

Previous work has shown that induction of a high-affinity NADPH-dependent nitrosodimethylamine demethylase (NDMAd) in liver microsomes occurs in rats due to fasting, ethanol consumption, and streptozotocin-induced diabetes. Several lines of observations suggest that this is due to the induction of specific cytochrome P-450 isozymes. Induction of P-450 species by ethanol has also been observed by other investigators. Since each of the above altered metabolic states has in common elevated levels of ketone bodies, the possible role of acetone, a known inducer of NDMAd, in the induction of the demethylase activity was investigated. Levels of endogenous acetone in fasted rats correlated (r = 0.72) with a three- to fourfold increase in NDMAd activity. However, a dose-response experiment showed endogenous levels of acetone to be capable of causing at most 40% of the induction in fasted rats. This suggests that other ketone bodies or factors may have contributed to the induction. The induction of NDMAd by ethanol was enhanced by alcohol dehydrogenase inhibitors pyrazole and acetaldehyde oxime, suggesting that ethanol, rather than its metabolites, was responsible for the induction.