21-aminosteroids prevent the down-regulation of hepatic cytochrome P450 induced by hypoxia and inflammation in conscious rabbits.
1 This study was conducted to assess whether a 21-aminosteroid, U74389G, could prevent the down-regulation of hepatic cytochrome P450 (P450) induced by acute moderate hypoxia or an inflammatory reaction. 2 The rabbits of two groups (n = 6 per group) were subjected to acute moderate hypoxia (PaO2 approximately 35 mmHg), one pre-treated with U74389G (3 mg kg-1 i.v. every 6 h, for 48 h). The rabbits of two other groups received 5 ml of turpentine s.c., one of them being pre-treated with U74389G (3 mg kg-1 i.v. every 6 h, for 72 h). The kinetics of theophylline (2.5 mg kg-1) were assessed to evaluate the activity of the P450. Once the rabbits were sacrificed, the P450 content and the amount of thiobarbituric acid reactive substances (TBARS), a marker of lipid peroxidation, were estimated in the liver. 3 Compared with control rabbits, hypoxia and inflammation increased theophylline plasma concentrations, as a result of a decrease in theophylline systemic clearance (P<0.05). Both experimental conditions reduced hepatic content of P450 by 40-50% (P<0.05) and increased the amount of hepatic TBARS by around 50% (P<0.05). Pre-treatment with U74389G prevented the hypoxia- and inflammation-induced decrease in theophylline systemic clearance, the down-regulation of hepatic P450, and the increase in liver TBARS. 4 It is concluded that in the rabbit, U74389G prevents hepatic P450 depression produced by acute moderate hypoxia and a turpentine-induced inflammatory reaction, possibly by eliciting a radical quenching antioxidant activity.
Galal
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A
Department of Pharmacology, Faculty of Medicine, University of Montréal, Montréal, Québec, Canada.
Souich
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P
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D015536:Down-Regulation / Q000187:drug effects*; D000860:Hypoxia / Q000201:enzymology*; D007249:Inflammation / Q000139:chemically induced / Q000201:enzymology*; D007509:Irritants; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D011281:Pregnatrienes / Q000494:pharmacology*; D011817:Rabbits; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014425:Turpentine
D000975:Antioxidants; D007509:Irritants; D011281:Pregnatrienes; D017392:Thiobarbituric Acid Reactive Substances; C074965:U 74389F; D003577:Cytochrome P-450 Enzyme System; D014425:Turpentine