Hepatic Drug-metabolizing Enzymes In Rats Research Articles

Ebselen protects against the reduction in levels of drug-metabolizing enzymes in livers of rats with deoxycholic acid-induced liver injury.

Ebselen is a seleno-organic compound that inhibits oxidative stress by lipid peroxidation through a glutathione peroxidase-like activity. We studied the effect of ebselen on the expression of hepatic drug-metabolizing enzymes in rats with deoxycholic acid-induced liver injury. Hydrophobic bile acids, such as deoxycholic acid, are known to cause cholestatic liver injury, and it was reported that expression of hepatic cytochrome P-450 (CYP) was reduced by deoxycholic acid administration in rats. Hydrophobic bile acids induce lipid peroxidation in the liver, and this may be one mechanism of the development of liver injury. In the present study, we investigated the effect of ebselen (30 mg/kg/day for 10 days) on rats ingesting deoxycholic acid (1% of diet for 10 days). Deoxycholic acid decreased levels of CYP1A1, 2B1, 2E1 and 3A2 to 34, 58, 62 and 37% of control values, respectively, and increased serum alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities to 1.8 and 8.6 times the levels of controls, respectively. Administration of ebselen with deoxycholic acid prevented the decreases in levels of CYP1A1 and 3A2 (86 and 65% of control, respectively) and the increases in serum ALP and ALT activities (1.4 and 1.9 times of control, respectively) caused by deoxycholic acid. These results indicate that ebselen may have a protective effect against hydrophobic bile acid-induced liver injury.

Modification of hepatic drug-metabolizing enzymes in rats treated with alkyl sulfides

Natural compounds which elevate detoxification enzymes and/or reduce activating enzymes could be considered as good candidates to protect against cancer. In this work, we studied the modulation of hepatic drug-metabolizing enzymes in rats treated with dimethyl sulfide (DMS), dimethyl disulfide (DMDS), methylpropyl disulfide (MPDS), dipropyl sulfide (DPS), dipropyl disulfide (DPDS) and diallyl disulfide (DADS) issued from Allium species. Compounds containing methyl groups had little or no effect. Compounds with two propyl groups or two allyl groups provoked a pleiotropic response on drug-metabolizing enzymes. DPS, DPDS and DADS induced ethoxyresorufin O-deethylase, methoxyresorufin O-demethylase and mostly pentoxyresorufin O-depentylase and decreased nitrosodimethylamine N-demethylase and erythromycin N-demethylase. These modifications of enzyme activities were accompanied by an increase of CYP 2B1,2 and a decrease of CYP 2E1, evidenced by immunoblotting. The same treatments stimulated some phase II enzyme activities such as glutathione transferase and UDP-glucuronyl transferases. This pattern of induction and/or inhibition of drug metabolizing enzymes was qualitatively similar to that elicited by the enzyme inducer, phenobarbital. The magnitude of the effects produced by DPDS was smaller than those produced by DADS and DPS. Our results suggest a possible protective effect of alkyl sulfides as well as diallyl disulfide, on the first step of carcinogenesis via the modulation of enzymes involved in carcinogen metabolism.

Studies on the Metabolic Fate of Cabergoline. (III): Identification of Liver Metabolites, Distribution of Brain, and Effect on Hepatic Drug-Metabolizing Enzymes in Rats.

The metabolites of cabergoline in liver were investigated in rats after a single oral administration. The identification was performed by HPLC and mass spectrometry equipped with an APCI interface. In addition to cabergoline, the identified metabolites are FCE-27395 which is the demethylated derivative of cabergoline and, possibly, one more demethylated of FCE-27395. Analysis of the metabolites in liver after a single oral administration of [14C]-cabergoline (0.5 mg/kg) showed a difference in the content of the metabolites between male and female rats. This sexual difference was due to the much higher content in FCE-27395 in male rat liver compared to female rat liver. For both sexes the major metabolite was FCE-27395, and other metabolites were found in minor quantities. The consecutive administration of cabergoline did not cause any induction of hepatic drug metabolizing enzymes, such as cytochrome P450, cytochrome b5, aniline hydroxylase, and aminopyrine demethylase. The distribution in the brain after a single intravenous administration of [3H]-cabergoline (0.5 mg/kg) was also investigated. The collected tissues were cerebral cortex, striatum, and hypophysis. The highest radioactivity was in the hypophysis, in which tissue the radioactivity tended to remain until 24 hour after dosing. Most of the radioactivity in these tissues could be attributed to cabergoline, as there were only traces of its metabolites.

Metabolism of gemcitabine in rat and dog.

1. The metabolism of 14C-gemcitabine in the male rat has been studied after intravenous administration of a single dose (10 mg/kg) or five doses (1 mg/kg/day) of 14C-gemcitabine. The metabolism in male dog has been studied after only single dosing. The effects of gemcitabine on hepatic drug-metabolizing enzymes in rat has also been studied. 2. The concentration of gemcitabine in the plasma was 11.84 micrograms/ml at 5 min, and then rapidly decreased after a single administration to rat. A deaminated uracil analogue of gemcitabine progressively increased with time. Gemcitabine and the uracil metabolite accounted for 80.0 and 11.8% of the radioactive dose in the 0-24-h urine samples respectively. Gemcitabine was the major component identified in lung, liver and kidney at 5 min after administration. 3. After repeated administration to rat, metabolites in the plasma and tissues were not remarkably different from those found after a single administration. 4. After a single administration to dog, the plasma concentration of gemcitabine was 12.39 micrograms/ml at 5 min. Gemcitabine and the uracil metabolite accounted for 8.3 and 71.8% of the dose in the 0-24-h urine samples respectively. 5. No differences were observed in enzymatic activities per whole liver between the gemcitabine-treated and control rat.

P-622 - Effects of Kampo medicine (Keigai-rengyo-to and Senkyu-chacho-san) on hepatic drug-metabolizing enzymes in rats.

P-622 - Effects of Kampo medicine (Keigai-rengyo-to and Senkyu-chacho-san) on hepatic drug-metabolizing enzymes in rats.

Modification of hepatic drug-metabolizing enzymes in rat fed naturally occurring allyl sulphides.

1. The effects of feeding allyl sulphides to rat (2000 ppm of the diet for 15 days) were investigated on various microsomal hepatic drug-metabolizing enzymes by their immunochemical detection and catalytic activity. 2. Allyl sulphides provoked a temporary dietary restriction, which enhanced the microsomal level of P450 and the activities of NADH-cytochrome c reductase and p-hydroxybiphenyl UDP-glucuronyltransferase (UDPGT 2), and lowered the activities of p-nitrophenol hydroxylase (PNPH), N-nitrosodimethylamine demethylase (NDMAD), laurate omega-hydroxylase (LAH) and glutathione S-transferase (GST). Therefore, pair-fed animals were used as a more relevant control for the dietary effects of allyl sulphides. 3. Diallyl sulphide (DAS) as well as diallyl disulphide (DADS) produced an enhancement of the microsomal level of P4501A2, 2B1/2 and 3A1/2, and epoxide hydrolase (EH) proteins, with an increase in the enzymatic activities they catalyse: ethoxyresorufin O-deethylase (EROD), aryl hydrocarbon hydroxylase (AHH), methoxyresorufin O-demethylase (MROD), ethoxycoumarin O-deethylase (ECOD), pentoxyresorufin O-depentylase (PROD), benzoxyresorufin O-debenzylase (BROD) and EH. Although P4502E1 proteins were lowered on treatment, NDMAD activity was not modified, and PNPH activity was even enhanced by allyl sulphides. Only DAS treatment raised erythromycin N-demethylase (ERDM) activity. 4. Both DAS and DADS increased the activity of GST and p-nitrophenol UDP-glucuronyltransferase (UDPGT 1), whereas UDPGT 2 activity was enhanced only by DAS.

Effect of red palm oil on some hepatic drug-metabolizing enzymes in rats

Red palm oil (RPO) from Elaeis guineensis is being considered for use as an edible oil in India as it is one of the richest natural sources of carotenoids. The effect of RPO on the host detoxification system, which is a vital mechanism in cancer prevention, was studied in three separate batches of Wistar/NIN inbred albino rats, and compared with controls, groundnut oil (GNO) and refined bleached deodorized palmolein oil (RBDPO). The first batch of 36 rats (12 from each group) comprised the adult males (26 wk old) of the third generation (F 2b) from a multigeneration reproduction study in which three groups were fed 10% GNO or RPO or RBDPO for three generations continuously. Phase II glutathione- S-transferase (GSH-T) activity was measured in the liver cytosol of these rats after they had twice completed the process of mating, gestation, lactation and weaning, because GSH-T is one of the principal detoxifying enzymes involved in conjugating reactions of phase II metabolism. The fourth generation (F 3b) weanling rats of the three groups, receiving GNO, RPO or RBDPO, were continued on the 10% oil diet for 9 wk, after which cytosolic GSH-T activity was measured. In the second experiment, eight male weanling Wistar/NIN inbred albino rats, 5 wk old, weighing 100–120 g, were fed 10% GNO, RPO or RBDPO for 4 wk in a 20% protein synthetic diet. Liver cytosolic GSH-T, reduced glutathione, microsomal total cytochrome P − 450, aminopyrine N-demethylase and ethoxyresorufin- O-deethylase activity were measured to elucidate the effect of RPO on some phase I and phase II reactions. Significantly higher levels of GSH-T were observed in F 2b and F 3b rats given RPO than in those given GNO or RBDPO. In the second experiment. GSH-T induction was also noted, together with increased levels of reduced GSH. Phase I enzymes and total cytochrome P − 450 levels were comparable between groups, indicating that no induction attributable to RPO had occurred. Thus, enhancement of one of the detoxifying phase II enzymes, in conjunction with the lack of induction of those activating phase I enzymes that are known to metabolize phenobarbitone and polycyclic aromatic hydrocarbons, suggests that RPO affords protection against chemical carcinogens, probably because of its carotenoid content.

Repression of cytochrome P450 by cytokines: IL-1 beta counteracts clofibric acid induction of CYP4A in cultured fetal rat hepatocytes.

Interleukin-1 is known to repress a number of hepatic drug-metabolizing enzymes in rats and humans. The effect of interleukin-1 beta on lauric acid 12-hydroxylase (CYP4A family) was studied in cultured fetal rat hepatocytes after clofibric acid induction. Dexamethasone was used as an agent promoting differentiation and long-term maintenance of active hepatocytes. Dexamethasone and clofibric acid in combination allowed maximal (13.5-fold) induction of CYP4A1. Lauric acid 12-hydroxylase activity was found to increase with time in culture. Interleukin-1 beta adversely affected P4504A clofibric acid-induced activity, totally eliminating the effect of induction at doses exceeding 5 ng/ml. This repression/inhibition was dose-dependent. The mechanism by which interleukin-1 beta prevents the development of cytochrome P4504A activity is unclear.

Induction of hepatic drug-metabolizing enzymes in rats treated with 1-nitropyrene

The inducing effects of 1-nitropyrene (1-NP) on the microsomal cytochrome P-450 system were studied in rats. Intraperitoneal administration of 1-NP led to increases in cytochrome P-450 content and aryl hydrocarbon hydroxylase, ethoxycoumarin, and ethoxyresorufin-O-deethylase activities. These increases were dose dependent. Cytochrome b5 content and aminopyrine and p-nitroanisole demethylase activities were not affected by treatment of rats with 1-NP. Substrate specificity, sensitivity to mixed-function oxidase inhibitors, and electrophoretic pattern of 1-NP-induced cytochrome(s) P-450 were compared to the major forms of cytochrome P-450 induced by phenobarbital and methylcholanthrene. Furthermore microsomes from 1-NP-induced rats showed greater ability to metabolize the chemical as compared with those from control animals; this result indicates that 1-NP induces a form(s) of cytochrome P-450 especially effective in the metabolism of the substance itself.

Formation of inactive cytochrome P-450 Fe(II)-metabolite complexes with several erythromycin derivatives but not with josamycin and midecamycin in rats

The effects of some macrolides (4mmoles·kg −1 p.o. daily for 4 days in vivo; 0.3mM in vitro) on hepatic drug-metabolizing enzymes in rats were compared. One group of macrolides including previously studied compounds (oleandomycin, erythromycin and troleandomycin), as well as several other erythromycin derivatives, showed induction of microsomal enzymes and formation of inactive cytochrome P-450-metabolite complexes in vivo; this formation increased in the order: oleandomycin, erythromycin ethylsuccinate, erythromycin stearate, erythromycin itself, erythromycin propionate, erythromycin estolate and troleandomycin. Troleandomycin and, to a lesser extent, erythromycin and oleandomycin formed cytochrome P-450-metabolite complexes when incubated in vitro with 1 mM NADPH and microsomes from rats pretreated with troleandomycin or phenobarbital, but not with microsomes from control rats or rats treated with 3-methylcholanthrene. In contrast, two other macrolides, josamycin and midecamycin, showed no induction of microsomal enzymes and no detectable formation of cytochrome P-450-metabolite complexes in vivo. In vitro, these macrolides failed to form detectable complexes even with microsomes from rats pretreated with troleandomycin or phenobarbital. Hexobarbital sleeping time was unaffected by preadministration of josamycin or midecamycin (4 mmoles·kg −1 p.o.) 2 hr earlier; the in vitro activity of hexobarbital hydroxylase was not inhibited by 0.3 mM josamycin or midecamycin. We conclude that, unlike several erythromycin derivatives, josamycin and midecamycin do not form inactive cytochrome P-450-metabolite complexes in rats.

Induction of hepatic drug-metabolizing enzymes in rats, dogs, and monkeys after repeated administration of an anti-inflammatory hexahydroindazole.

The effect of repeated administration of an anti-inflammatory hexahydroindazole, (+/-)-3,3 alpha,4,5,6,7-hexahydro-2-[3-(4-morpholinyl)-propyl]-3-phenyl-7-(phenylmethylene)-2H-indazole (HMPPI), on hepatic microsomal drug-metabolizing enzymes in rats, dogs and monkeys was studied. Dose-dependent increases in the ratio of liver weight to body weight were observed in all three species. Microsomal protein concentration increased in rats and monkeys but not in dogs. Cytochrome P-450 concentration and aminopyrine N-demethylase activity increased in all species. Aniline hydroxylase activity increased only in dogs. In all three species, the largest increase in all parameters, except for the liver weight/body weight ratio, was observed in animals on the intermediate dose (50 mg/kg per d) of the hexahydroindazole, probably of the toxicity of the hexahydroindazole at the high dose (250 mg/kg per d).

Effect of vitamin A deficiency on the pulmonary and hepatic drug-metabolizing enzymes in rat.

The effect of vitamin A deficiency on the drug-metabolizing enzyme system of the lung and liver was analyzed in rats fed diets with or without vitamin A for 5-6 weeks. The hepatic level of vitamin A was significantly reduced in vitamin A deficient animals. The hepatic cytochrome P-450 and b5 contents and activity of benzo(a)pyrene hydroxylase was significantly reduced in deficient animals. Contrary to this, pulmonary cytochrome P-450 and b5 contents were above the control values. No alteration in pulmonary benzo(a)pyrene hydroxylase was noted. The uridine diphosphate-glucuronosyltransferase activity of digitonin-treated microsomal membranes was below the control values both in lung and liver. However, the native uridine diphosphate-glucuronosyltransferase activity remained unchanged in the liver and was below control values in the lung.

Consumption of poisonous plants ( Senecio jacobaea, symphytum officinale, pteridium aquilinum, hypericum perforatum) by rats: Chronic toxicity, mineral metabolism, and hepatic drug-metabolizing enzymes

Effects of dietary tancy ragwort ( Senecio jacobaea), comfrey ( Symphytum officinale), bracken ( Pteridium aquilinum) and alfalfa ( Medicago saliva) on hepatic drug-metabolizing enzymes in rats were measured. Tansy ragwort and bracken increased ( P < 0.05) the activity of glutathione transferase and epoxide hydrolase. Comfrey and alfalfa increased ( P < 0.05) the activity of aminopyrine N-demethylase. Feeding bracken or St. John's wort ( Hypericum perforatum) in conjunction with tansy ragwort did not influence chronic toxicity of tansy ragwort as assessed by rat survival time. Dietary tansy ragwort resulted in increased ( P < 0.05) hepatic copper levels; the other plants did not affect copper levels. The results do not suggest any major interaction in the toxicity of tansy ragwort with bracken or St. John's wort.

Sex-related differences in the impairment of hepatic drug-metabolizing enzymes in rats with adjuvant disease

1.1. We have studied the optimum conditions for the induction of adjuvant carrageenan-induced inflammation (ACII) in male Wistar rats with limited susceptibility to adjuvant arthritis (AA).2.2. ACII was induced by intradermal injection of Freund's complete adjuvant (CFA), containing 10 mg/ml Mycobacterium tuberculosis, followed by a subplantar inoculation of the nonspecific inflammatory stimulus carrageenan at different times.3.3. Data obtained indicate that the arthritis of rats inoculated with CFA is significantly increased by carrageenan, particularly when it is injected 14 days after the adjuvant. Arthritis enhancement was more evident in the joints of the leg that had been previously injected with carrageenan, and remained stable around the peak level for some weeks. The development of joint inflammation was associated histologically with the appearance of inflammatory cells in the synovial membrane of those animals.4.4. We found that the injection of carrageenan aggravated the course of AA in general, but very significantly when administered at the moment of the appearance of arthritis (day + 14). This aggravation affected both the intensity of inflammation and the chronicity of the disease.