The effects of α,β-unsaturated aldehydes on hepatic thiols and thiol-containing enzymes

The effects of series of α,β-unsaturated aldehydes on hepatic glutathione, cytochrome P450, and NADPH-cytochrome c reductase activity were compared with time. Male F-344 rats were dosed with muconaldehyde (36 μmol/kg), acrolein (89 μmol/kg), crotonaldehyde (450 μmol/kg), or the saturated aldehyde propionaldehyde (89 μmol/kg) and terminated 0.5, 4, or 24 hr later. Acrolein or muconaldehyde reduced glutathione to 51 and 75% of controls, respectively, at 4 hr; glutathione returned to control values at 24 hr. Only at 24 hr, acrolein, muconaldehyde, or crotonaldehyde decreased cytochrome P450 to 61, 71, and 67% of control values, respectively; ethylmorphine N-demethylation was decreased to a greater extent, i.e., to 35, 60, and 23% of controls. The reductase activity was unchanged at any time following the treatment with reactive aldehydes which were not hepatotoxic (as shown by glucose 6-phosphatase activity, histological changes, or serum enzymes). Propionaldehyde changed none of these activities. Acrolein (44.5 μmol/kg) given 4 hr prior to phenobarbital (50 mg/kg) for two consecutive days decreased the phenobarbital induction of cytochrome P450 to 45% of phenobarbital alone. This treatment also decreased the 2α, 2β, 6β, 16α, and 16β hydroxylation of testosterone as well as androstenedione formation showing effects on individual cytochrome P450 isozymes. NADPH-cytochrome c reductase induction was not decreased by this treatment, thus indicating that in vivo these changes are due to a mechanism other than generalized inhibition of protein synthesis.