Comparison of the effects of piperine administered intragastrically and intraperitoneally on the liver and liver mixed-function oxidases in rats

Piperine, a major pungent constituent of black and red peppers, was administered to rats intragastrically and intraperitoneally to study whether it alters the activities of hepatic mixed-function oxidases (MFO) and serum enzymes as specific markers of hepatotoxicity. An intragastric dose of 100 mg/kg of piperine to adult, male Sprague-Dawley rats caused an increase in hepatic microsomal cytochrome P-450 and cytochrome b5, NADPH-cytochrome c reductase, benzphetamine N-demethylase, aminopyrine N-demethylase and aniline hydroxylase 24 h following treatment. On the other hand, a 10 mg/kg dose given i.p. exhibited no effect on the activities of the aforementioned parameters of the hepatic drug-metabolizing enzyme system. However, when the intragastric and intraperitoneal doses were increased to 800 mg/kg and 100 mg/kg, respectively, the black pepper alkaloid produced a significant decrease in the levels of cytochrome P-450, benzphetamine N-demethylase, aminopyrine N-demethylase and aniline hydroxylase 24 h after treatment. None of the treatments significantly elevated the activities of serum sorbitol dehydrogenase (SDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and isocitrate dehydrogenase (ICD), suggesting that piperine is not a hepatotoxic agent.     

Stimulatory and inhibitory effects of dimethyl sulfoxide on microsomal aniline hydroxylase activity

Dimethyl sulfoxide (DMSO) at a single dose of 3 ml/kg body wt, administered i.p. to male rats, caused a significant increase in the hepatic microsomal aniline hydroxylase activity. However, the level of cytochrome P-450, the activities of NADPH-cytochrome c reductase, benzphetamine N-demethylase and aminopyrine N-demethylase were unchanged at 24 h post-treatment. DMSO interacted with control rat liver microsomes in vitro and produced a type II spectral change (peak at 420 nm and trough at 392 nm). On the other hand, liver microsomes from DMSO-treated rats gave qualitatively similar spectra, but with a higher magnitude of binding. Liver microsomes from DMSO-treated rats showed a 3.4-fold increase in Vmax for aniline hydroxylase, while Km was found to be the same when compared with control rat liver microsomes. In vitro addition of 6 mM DMSO to microsomal incubations from control and DMSO-treated rats caused a 9-fold and a 25-fold increase in Km, respectively, while Vmax values for aniline hydroxylase were unchanged. When DMSO (6 mM) was incubated with rat liver microsomes in the presence of NADPH, there was formation of formaldehyde. The results suggest an interaction of DMSO with microsomal cytochrome P-450.     

Lack of in vitro and in vitro effects of fenbendazole on phase I and phase II biotransformation enzymes in rats, mice and chickens.

Intraperitoneal administration of 10 mg fenbendazole/kg bw daily for 5 d caused no significant alterations in the activities of hepatic microsomal drug-metabolizing enzymes viz aminopyrine N-demethylase, aniline hydroxylase and cytosolic glutathione S-transferase in rats, mice and chickens. Similarly no significant difference in the amount of microsomal cytochrome P-450 and NADPH-cytochrome c reductase was found between control and treated animals. In vitro incubation of fenbendazole with rat, mouse and chicken microsomes suggests that the drug neither binds to microsomal protein cytochrome P-450 nor inhibits the activities of aminopyrine N-demethylase and aniline hydroxylase. Similarly in vitro addition of fenbendazole to cytosolic glutathione S-transferase from the above species did not alter the activity of this enzyme. The results indicate that fenbendazole does not alter the activity of hepatic microsomal monooxygenase system significantly in rats, mice and chickens at a dosage level of 10 mg/kg body weight. In vitro studies also indicate that fenbendazole does not interact with the hepatic microsomal monooxygenase system, indicating it is not a substrate for cytochrome P-450-dependent monooxygenase system.     

Differences in the effects of piperine and piperonyl butoxide on hepatic drug-metabolizing enzyme system in rats

An i.p. administration of rats with piperine (100 mg/kg) and piperonyl butoxide (400 mg/kg) produced a significant decrease in hepatic cytochrome P-450, and activities of benzphetamine N-demethylase, aminopyrine N-demethylase and aniline hydroxylase 1 hr after the treatment. Twenty-four hr later, these parameters along with cytochrome b5 and NADPH-cytochrome c reductase remained depressed only in piperine-treated rats. In contrast, piperonyl butoxide caused a significant induction of these parameters with the exception of cytochrome b5 and aminopyrine N-demethylase, which were up by 36 and 33% over their respective controls but not significantly. These results point up that effect of piperine on hepatic mixed-function oxidases is monophasic while that of piperonyl butoxide is biphasic.     

Hepatic mixed-function oxidase activities of wild pigeons

Hepatic mixed-function oxidase activities of wild pigeons were determined and compared with those of rat to assess the apparent differences in avian and mammalian drug metabolism. Aminopyrine N-demethylase, benzphetamine N-demethylase, ethylmorphine N-demethylase, aniline hydroxylase, NADPH-cytochrome c reductase, glutathione S-transferase activities and cytochrome P-450 levels in pigeon liver were 30-80% lower than the corresponding activities in rat liver. p-Nitroanisole O-demethylase activity in pigeon liver was similar to that of rat liver. Wild pigeon-liver benzo[a]pyrene hydroxylase activity was approx. five times higher than that in the rat. Pigeons did not reveal any noticeable sex differences in mixed-function oxidase activities. Administration of 3-methylcholanthrene and phenobarbital to pigeons resulted in the induction of demethylase and benzo[a]pyrene hydroxylase activities and in cytochrome P-450 levels.     

Differences in the Effects of Piperine and Piperonyl Butoxide on Hepatic Drug-Metabolizing Enzyme System in Rats

ABSTRACT

An i.p. administration of rats with piperine (100 mg/kg) and piperonyl butoxide (400 mg/kg) produced a significant decrease in hepatic cyotchrome P-450, and activities of benzphetamine N-demethylase, aminopyrine N-demethylase and aniline hydroxylase 1 hr after the treatment. Twenty-four hr later, these parameters along with cytochrome b5 and NADPH-cytochrome c reductase remained depressed only in piperine-treated rats. In contrast, piperonyl butoxide caused a significant induction of these parameters with the exception of cytochrome b5 and aminopyrine N-demethylase, which were up by 36 and 33% over their respective controls but not significantly. These results point up that effect of piperine on hepatic mixed-function oxidases is mono-phasic while that of piperonyl butoxide is biphasic.     

Sex difference in responsiveness to Aztreonam of monooxygenase system in liver microsomes from rats

Effect of successive administration of Aztreonam on microsomal monooxygenase system was investigated in male and female Sprague-Dawley rats. The activities of benzphetamine N-demethylase, aminopyrine N-demethylase, p-nitroanisole O-demethylase and aniline hydroxylase in liver microsomes from male rats were decreased dose-dependently by Aztreonam. On the contrary, the activities in liver microsomes from female rats were slightly increased rather than decreased by the administration of Aztreonam. In addition, Aztreonam was found to decrease the specific content of microsomal cytochrome P-450 in male rats but not in female rats. The decreases in the activities observed in male rats were accompanied by a parallel decrease in the specific content of cytochrome P-450. Furthermore, the results of quantitation of P-450 (M-1), one of the male specific forms of cytochrome P-450, indicated that the administration of Aztreonam resulted in a dose-dependent decrease in the content of P-450 (M-1) in liver microsomes from male rats.     

Isopropanol enhancement of cytochrome P-450-dependent monooxygenase activities and its effects on carbon tetrachloride intoxication

Acute or chronic treatment of rats with isopropanol caused a significant increase in hepatic cytochrome P-450 content and a two- to threefold increase in aniline hydroxylase and 7-ethoxycoumarin O-deethylase activities, but no significant change in ethylmorphine N-demethylase or benzo(a)pyrene hydroxylase activity. In rats treated with isopropanol and challenged with CCl4, liver toxicity of CCl4 was characteristically potentiated, as assessed by elevation of serum glutamic-pyruvic transaminase (SGPT) levels. Isopropanol pretreatment also potentiated CCl4-induced damage to the hepatic monooxygenase system. In addition to a decrease in cytochrome P-450, rats treated with isopropanol and challenged with CCl4 showed a nonspecific decrease not only in aniline hydroxylase and 7-ethoxycoumarin O-deethylase activities, but also in ethylmorphine N-demethylase, benzo(a)pyrene hydroxylase, and NADPH-cytochrome c reductase activities. These results were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized microsomes. The electrophoretic results showed that isopropanol pretreatment markedly potentiated the CCl4-caused destruction of cytochrome P-450 hemeproteins. The data strongly suggest that isopropanol increases one or more forms of cytochrome P-450 which selectively enhance the metabolism of CCl4 to an active metabolite. This active metabolite then causes a nonselective damage to the microsomal mixed-function oxidase system.     

Induction of hepatic microsomal drug metabolizing enzyme system by levamisole in male mice

To examine the effect of levamisole on the hepatic drug metabolizing enzyme system of mice, levamisole at a dose of 20 mg kg-1 day-1 was administered i.p. for 5 days. Compared with the control values, the levamisole treatment significantly increased the amount of cytochrome P450 and cytochrome b5 and the in-vitro activities of aminopyrine N-demethylase, benzphetamine N-demethylase and aniline hydroxylase. In contrast, there was no change in microsomal NADPH-cytochrome c reductase activity in-vitro or in the relative liver weight and microsomal protein content compared with the corresponding values for control mice. Furthermore, in-vivo induction of drug metabolism was demonstrated by decreased pentobarbitone sleeping times after levamisole pretreatment. These results indicate that certain hepatic microsomal mixed function oxidases of mice are induced by levamisole, the drug that is frequently used as an anthelmintic in veterinary medicine and as an immunostimulant drug in human medicine.     

Selective inactivation of rat lung and liver microsomal NADPH-cytochrome c reductase by acrolein

Addition of acrolein to rat lung or liver microsomal suspensions resulted in total inactivation of NADPH-cytochrome c reductase and partial conversion of cytochrome P-450 to P-420 in a concentration- and time-dependent fashion. Acrolein also caused total loss of nonprotein sulfhydryl content in both preparations, whereas protein sulfhydryl content was decreased by 40% and 28% in lung and liver preparations, respectively. Maxima of about 60% of the total lung cytochrome P-450 and 50% of the liver cytochrome P-450 in acrolein-treated microsomes did not support the N-demethylation of benzphetamine or ethylmorphine or hydroxylation of aniline because of the total loss of NADPH-cytochrome c reductase. Addition of purified NADPH-cytochrome c reductase to the acrolein-treated lung or liver microsomal suspension largely restored these monooxygenase activities. Addition of glutathione or dithiothreitol to the lung or liver microsomal suspension prior to the addition of acrolein significantly protected cytochrome P-450 from conversion to cytochrome P-420 as well as NADPH-cytochrome c reductase from inactivation. Thus, selective conjugation of acrolein with lung and liver NADPH-cytochrome c reductase but not cytochrome P-450 was responsible for total loss of these lung and liver monooxygenase activities.     

Endotoxin- and inflammation-induced depression of the hepatic drug metabolism in rats

Carrageenan-induced inflammation and exposure to endotoxin considerably decreased the content of cytochrome P-450 and activities of ethylmorphine N-demethylase and meperidine N-demethylase, but did not decrease the activities of aniline hydroxylase or NADPH-cytochrome c reductase, compared with the respective activities in rats treated with carrageenan alone. These results suggest that under these experimental conditions, the two host-related environmental factors interact and enhance a decrease in rat hepatic microsomal drug metabolizing enzymes depending on the substrate used.     

Studies on the effect of chronic consumption of moderate amounts of ethanol on male rat hepatic microsomal drug-metabolizing activity

Weanling, male Sprague-Dawley rats given 10% ethanol in the drinking water and food ad lib. for up to 8 weeks consumed 17% of their calories as ethanol. The alanine aminotransferase (ALT), aspartate aminotransferase (AST), and liver histology by light microscopy were unaffected by this treatment. Similarly, hepatic microsomal NADPH-cytochrome c reductase, ethylmorphine N-demethylase and benzphetamine N-demethylase activities were also not affected by ethanol consumption. On the other hand, cytochrome P-450 content, aniline hydroxylase activity and acetaminophen metabolism as measured by both the cysteine conjugate and the [3H]acetaminophen covalently-bound to microsomal protein were increased significantly by ethanol consumption. The maximal effect was seen by 6 weeks. The 2- to 3-fold increase in aniline and acetaminophen metabolism, the absence of liver damage, and the similarity in weight gains and caloric intakes for controls and treated animals suggest that the rat on 10% ethanol in the drinking water is a reasonable model for studies of the effect of moderate alcohol consumption on specific biochemical pathways.     

Alterations in hepatic Phase I and Phase II biotransformation enzymes by garlic oil in rats

Studies were conducted to examine the effect of a single and repeated administrations of garlic oil (diallyl sulfide) on Phase I and Phase II biotransformation enzymes in rats. Adult, male Sprague-Dawley rats treated with a single dose of garlic oil (500 mg/kg i.p.) showed a significant depression of hepatic cytochrome P-450, aminopyrine Ndemethylase and aniline hydroxylase while microsomal protein content, cytochrome b₅, NADPH-cytochrome c reducase, benzphetamine N-demethylase and cytosolic glutathione, S-transferase remained unaffected 24 h following the treatment. Although certain microsomal enzymes were depressed, there was no liver damage caused by garlic oil as judged by the putative serum enzyme test. On the other hand, daily administration of garlic oil (50 mg/kg) i.p. for 5 days) produced a significant increase in hepatic cytochrome P-450, aminopyrine N-demethylase and benzphetamine N-demethylase activities, but not in the rest of the aforementioned parameters of biotransformation reactions. These data indicate that the effect of garlic oil on the hepatic drug-metabolizing enzyme system is dose-dependent.     

Studies on possible sulfadimethoxine toxicity to liver and liver drug metabolizing enzyme system of goats, quail and rats

No significant increases in serum SDH, ALT and AST activities were observed in goats and rats receiving oral sulfadimethoxine at 5 times the therapeutic dose. The quail showed significantly higher activities of SDH and ALT when compared to control values. Moderate increases in liver microsomal cytochrome P-450 and aniline hydroxylase activity were observed in goats and quail but no appreciable change in benzphetamine N-demethylase activity was detected in any species. These results suggest a lack of hepatic toxicity of sulfadimethoxine to these species under the reported experimental conditions.     

年龄对大鼠肝脏生物转化功能及膜流动性的影响

通过与青年(3～4月)及中年(14月)组比较,研究了老年(24月)大鼠肝脏生物转化酶活性改变及膜流动性变化。结果表明,老年大鼠肝微粒体P-450含量、NADPH-细胞色素C还原酶活性无明显改变,但氨基比林N-脱甲基酶、苯胺羟化酶活性明显降低,且微粒体及胞浆GST、胞浆GSH-Px活性也明显下降;同时肝微粒体膜脂区流动性明显降低,膜Ch/PL值显著增大。研究提示,微粒体膜脂质环境及流动性变化与上述生物转化功能改变可能有一定的联系。     

Suppression of the hepatic microsomal cytochrome P-450 dependent mixed function oxidase activities in golden hamster during Leishmania donovani infection

Experimental infection of golden hamsters with Leishmania donovani caused significant alterations in the hepatic microsomal mixed function oxidase system. Gross examination of liver indicated hepatomegaly. Microsomal protein contents were only marginally elevated. Cytochrome P-450 as well as haem contents were significantly decreased and it directly correlated with the degree of infection. Cytochrome b5 exhibited elevation at lower degrees of infection which came down to control levels at the peak infection. Concomitant suppression was also noticed in cytochrome P-450 dependent monooxygenase activities, viz. aniline hydroxylase, benzo[a]pyrene hydroxylase and aminopyrine N-demethylase. No significant change was observed in NADH-cytochrome b5 reductase and NADPH-cytochrome c reductase. The results indicate suppression of hepatic microsomal MFO activities during visceral leishmaniasis.     

Age-and sex-related differences in rat liver microsomal enzymes and their inducibility by toluene

In the liver microsomes of toluene-treated and control Sprague-Dawley rats (n = 148, males and females aged 13-93 days), the contents of cytochrome P-450 and b5 and the activities of NADPH-cytochrome c reductase and four monooxygenases were studied. In male control rats, cytochrome contents and NADPH-cytochrome c reductase, aminopyrine N-demethylase and aniline hydroxylase activities increased to the age of one month, and after a slight decrease in cytochrome concentrations, the average adult level was reached by the age of two months. Aniline hydroxylase and 7-ethoxycoumarine O-deethylase activities decreased to about half at the same age period. In control female rats, the activities of aminopyrine N-demethylase and aniline hydroxylase decreased after the age of one month, and they remained at a considerably lower level in adult females than in males. The sex-dependence of other enzymes was negligible. Toluene induction was already well developed in the youngest age group of both sexes; in most cases the induced enzyme levels in young rats were as high or higher than in adults. In adult female rats, toluene induction of all enzymes was weaker than in males. In male rats, the toluene-induced level of aniline hydroxylase and 7-ethoxycoumarine O-deethylase showed deep minima at the age of 43-53 days, at the puberty of rats.     

The interaction between two forms of cytochrome P-450 during drug oxidation in the reconstituted system containing limited amount of NADPH-cytochrome P-450 reductase

The activities of drug oxidation in a reconstituted system which contains two forms of cytochrome P-450 and a limiting amount of NADPH-cytochrome P-450 reductase were determined. Cytochrome P-450 (termed MC P-4481 and MC P-4482) purified from liver microsomes of 3-methyl-cholanthrene-treated rats was active in both 2- and 4-hydroxylation of biphenyl but cytochrome P-450 (termed PB P-450) purified from liver microsomes of phenobarbital-treated rats was active in 4-hydroxylation of biphenyl only. PB P-450, MC P-4481 and MC P-4482 were most active toward benzphetamine N-demethylation, aniline hydroxylation and 7-ethoxycoumarin O-deethylation, respectively. PB P-450 inhibited the activity of biphenyl 2-hydroxylation supported by MC P-4481 or MC P-4482. On the contrary, no inhibition of PB P-450 supported benzphetamine N-demethylation was observed when MC P-4481 or MC P-4482 was added to the system containing PB P-450 and limited amount of the reductase. The apparent Km of PB P-450 for the reductase obtained from double reciprocal plot of the reductase concentration and the activity of biphenyl hydroxylase or benzphetamine N-demethylation was lower than that of MC P-4481 or MC P-4482. These and other results suggest that there is a certain hierarchy among the cytochrome P-450 species for receiving electrons from reductase.     

培氟沙星对大鼠肝微粒体酶系的抑制作用

大鼠经培氟沙星４００ｍｇ／ｋｇ，ｉｇ，ｑｄ×７ｄ后，肝微粒体酶系中的细胞色素ｂ５、氢基比林－Ｎ－脱甲基醉，７－乙氧基香豆素－Ｏ－脱乙基酶及苯并芘羟化酶含量显著减少，细胞色素Ｃ还原酶活性降低，但细胞色素Ｐ－４５０、乙基吗啡－Ｎ－脱甲基酶、戊巴比妥侧链羟化酶活性无改变。表明培氟沙星有抑制大鼠肝微粒体酶系中一些酶的活性。     

Effect of successive administration of zopiclone, a new class of minor tranquillizer, on mouse liver microsomal mono-oxygenase system

Oral administration of zopiclone to mice (10 mg/kg daily) for 14 days had no significant effect on body weight, liver weight, hepatic microsomal protein or cytochrome P-450 contents but produced significant increases in the activities of NADPH-cytochrome c reductase, NADH-ferricyanide reductase, aniline hydroxylation and aminopyrine N-demethylation.