Kinetic Studies for Aniline Hydroxylase After Prolonged Ethanol Treatment

Nakanishi, Suehiro; MASAMURA, Eiko; Tsukada, Miyoko; Matsumura, Riichiro

doi:10.1254/jjp.21.303

Cited by 35 publications

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“…These were exposed to a daily sched ule of 12-hr light and 12-hr darkness. All had free access to adequate laboratory chow (CLEA, CE-2), and ethanol treatments were the same as in the previous experiments (1,2). In the present experiments, the rats were sacrificed 5 to 6 months after the beginning of ethanol treatments and the hepatic aniline hydroxylase and aminopyrine demethylase activities, microsomal cytochrome P-450 and phospholipid phosphorous contents were determined.…”

Section: Methodsmentioning

confidence: 99%

“…The reaction mixtures were in cubated in 30 ml Erlenmeyer flasks in an atmosphere of air with a Dubnoff metabolic shaker at 37°C for 10 min. The p-hydroxylation of aniline was estimated from p-aminophenol formation, with the amount of p-aminophenol being determined as described previously (2).…”

Section: Methodsmentioning

confidence: 99%

“…1.5-fold increased, compated with that of controls, in spite of no change being detected in hexobarbital oxidase and aminopyrine demethylase activities (1,2).<BR> It is known that pretreatment of rats with phenobarbital markedly increases the activities of several hepatic drug-metabolizing enzymes in smooth-surfaced microsomes relative to rough-surfaced ones. The ratio of enzyme activity in smooth microsomes to that in rough microsomes increases in the liver from the phenobarbital-treated animal as compared with that from the control animal (3,4).…”

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Metabolism of Drugs by Subfractions of Hepatic Microsomes From Prolonged Ethanol-Treated Rats

et al. 1972

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In a previous paper, it was reported that in rats treated chronically with ethanol, the side-chain oxidation of hexobarbital, N-demethylation of aminopyrine and p-hydroxylation of aniline in vitro from either 9,000 g supernatant; fraction of liver homogenates or washed microsomes was identical with that of control rats when ethanol was withdrawn and subst ituted for tap water 24 hr prior to sacrifice. In contrast, the activity of aniline hydroxylase of the rats which continued to ingest ethanol ad libitum up to the time of sacrifice was approx.1.5-fold increased, compated with that of controls, in spite of no change being detected in hexobarbital oxidase and aminopyrine demethylase activities (1, 2).
It is known that pretreatment of rats with phenobarbital markedly increases the activities of several hepatic drug-metabolizing enzymes in smooth-surfaced microsomes relative to rough-surfaced ones. The ratio of enzyme activity in smooth microsomes to that in rough microsomes increases in the liver from the phenobarbital-treated animal as compared with that from the control animal (3, 4). Fouts and Gram (5) reported that ratios of smooth versus rough-surfaced microsomal aminopyrine N-demethylase and hexobarbital oxidase of rabbits decreased after 3-methylcholanthrene treatment.
The present experiments were conducted to determine the intramicrosomal distribution of drug-metabolizing enzyme activity in the rats treated chronically with ethanol. Parallel experiments were done to determine the intramicrosomal distributions of cytochrome P-450, protein and phospholipid phosphorous contents of the liver from the rats treated chronically with ethanol. METHODSMale Wistar rats weighing 80 g initially were used. These were exposed to a daily sched ule of 12-hr light and 12-hr darkness. All had free access to adequate laboratory chow (CLEA, CE-2), and ethanol treatments were the same as in the previous experiments (1, 2). In the present experiments, the rats were sacrificed 5 to 6 months after the beginning of ethanol treatments and the hepatic aniline hydroxylase and aminopyrine demethylase activities, microsomal cytochrome P-450 and phospholipid phosphorous contents were determined. According to the drinking fluid, the animals were divided into two groups, one drinking tap water (control group), and the other only ethanol (ethanol group). The rats of ethanol group were given 10 v/v % ethanol for the final week prior to sacrifice. For the enzyme assay, the latter was further divided into two subgroups. In one, ethanol was withdrawn ands ubstituted for tap water 24 hr prior to sacrifice (EtOH-1), whereas in the other, the animals continued to drink ethanol adlibitum up to the time of sacrifice (EtOH 2). All the animals were deprived of food 12 hr prior to sacrifice to reduce glycogen contents in the liver, and sacrificed by decapitation between 8 : 30 and 9 : 00 a.m. to mini mize the circadian variations of drug-metabolizing enzyme activities (6).The procedure of microsomal subfractionation was essentially that o...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 85%

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Metabolism of Drugs by Subfractions of Hepatic Microsomes From Prolonged Ethanol-Treated Rats

et al. 1972

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“…The p-hydroxylation of aniline was determined by measuring the p-aminophenol produc tion as described previously (13). The protein contents in 9,000 g supernatant fractions and microsomes were determined by the method of Lowry et a].…”

Section: Malementioning

confidence: 99%

Effect of Type I Compounds on P-Hydroxylation of Aniline in Vitro

et al. 1972

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During the past fifteen years, it has become evident that a variety of lipid soluble drugs such as aniline, aminopyrine and hexobarbital are oxidized by NADPH-dependent enzymes in hepatic microsomes (1-4). Cytochrome(s) P-450 plays a critical role as the terminal oxidase in the metabolism of drugs, steroids and heme (5-7). It is generally accepted that the hepatic drug-metabolizing enzyme system has few specificities for substrates but recent studies have suggested the existence of more than two microsomal enzymes which metabolize the drugs (8, 9).
On the other hand, the addition of various substrates of microsomal mixed-function oxidase system to aerobic liver microsomes causes two types of spectral change. One class of spectral change (termed type I) is characterized by the appearance of a trough at 420 mμand an absorption peak at 385 mμ. Aminopyrine, hexobarbital, chlorpromazine, SKF 525-A and DDT cause type I spectral change. Another class of spectral change (termed type II) is characterized by the appearance of a trough at 392 mμ and an absorption peak at 430 mμ. Aniline, nicotinamide, pyridine and p-aminophenol cause type II spectral change (10).
Drug interaction with endoplasmic reticulum occurs not only to constitute enzyme substrate complex but also to modify the physical properties, amounts, composition and turnover of constitutive membrane components (11). At present aniline is thought to bind to the CO-binding site of cytochrome P-450, whereas aminopyrine or hexobarbital is thought to bind to the lipids of the endoplasmic reticulum or hydrophobic region cytochrome P-450 (12).
The present paper concerns the effects of type I binders such as aminopyrine, hex obarbital and chlorpromazine on p-hydroxylation of aniline in vitro. METHODS Male

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“…Ethanol treatment and preparation of liver microsomes were the same as described previously (5). Rats of the ethanol group were given ethanol solution as drinking fluid ad libituni prior to sacrifice.…”

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Activities of Hepatic Microsomal Electron Transport System in Prolonged Ethanol-Treated Rats

Nakanishi

Shiohara

Tsukada

et al. 1975

Japanese Journal of Pharmacology

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In previous studies, the authors reported that chronic ethanol feeding caused an in crease in the amount of cytochrome P-450 and stimulated the 1~-hydroxylation of aniline, but had no effect on the N-demethylation of aminopyrine or the side-chain oxidation of hexobarbital by liver microsomes (1) (2). Holtzman et al. (3) pointed out that the N demethylation of ethylmorphine by liver microsomes was more closely related to NADPH cytochrome P-450 reductase activity than to the amount of cytochrorne P-450. On the other hand, it has recently been revealed that cytochronie P-450 reductase activity de creases in the presence of aniline and increases in the presence of aminopyrine (4).Thus in the present study, activities of main components of hepatic microsomal elec tron transport system in prolonged ethanol-treated rats were determined in the presence of the drug substrate.

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Kinetic Studies for Aniline Hydroxylase After Prolonged Ethanol Treatment

Abstract: In the previous paper, we reported of rats treated chronically with ethanol; that side chain oxidation of hexobarbital, N-demethylation of aminopyrine and p-hydroxylation

Cited by 35 publications

References 7 publications

Metabolism of Drugs by Subfractions of Hepatic Microsomes From Prolonged Ethanol-Treated Rats

Metabolism of Drugs by Subfractions of Hepatic Microsomes From Prolonged Ethanol-Treated Rats

Effect of Type I Compounds on P-Hydroxylation of Aniline in Vitro

Activities of Hepatic Microsomal Electron Transport System in Prolonged Ethanol-Treated Rats

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