The changes in the hepatic drug metabolizing enzymes induced by the liver tumor promoter thiobenzamide (TB) were investigated. Feeding of TB to rats at a promoting regimen (1 g/kg of diet for 2 weeks) resulted in a significant decrease in the amount of liver microsomal cytochrome P-450 and of total heme. Also, the activity of cytochrome P-450 dependent monooxygenases (aminopyrine demethylase, arylhydrocarbonmonooxygenase and ethoxycoumarindeethylase) and FAD-containing monoxygenase (N,N-dimethylaniline N-oxidase and TB S-oxidase) were depressed. By contrast, phase II enzymes such as epoxide hydrase, UDP-glucuronyl transferase and GSH-transferase were significantly induced. This overall change in the drug metabolizing system was associated with tolerance of the liver towards a high necrogenic dose of TB itself as well as with an increase of mitoses and apoptosis of the hepatocytes. The findings suggest a possible relationship between this TB-induced adaptive response and the promoting activity of the compound on liver carcinogenesis.
Autori interni: | ||
Autori: | Chieli E; Saviozzi M; Malvaldi G. | |
Titolo: | Changes in the rat liver drug metabolizing system during a short thiobenzamide feeding cycle. | |
Anno del prodotto: | 1987 | |
Appare nelle tipologie: | 1.1 Articolo in rivista |