Inhibition of microsomal cytochrome c reductase activity by a series of α,β-unsaturated aldehydes

α,β-Unsaturated aldehydes are reactive and cytotoxic compounds which occur in the environment and are also formed in vivo. Many of these aldehydes have been reported to inhibit hepatic cytochrome P-450. Our laboratory has shown that trans,trans-muconaldehyde (a possible metabolite of benzene) as well as acrolein and crotonaldehyde, when added to hepatic microsomes, decreased cytochrome P-450 (measured spectrophotometrically). Additional studies showed that several α,β unsaturated aldehydes also inhibited hepatic microsomal NADPH-cytochrome c reductase. Acrolein, crotonaldehyde and trans,trans-muconaldehyde all decreased NADPH-cytochrome c reductase activity in vitro. Concentrations of 0.5, 1.0 and 1.5 mM acrolein decreased activity to 60, 26 and 11% of control respectively. Similar concentrations of trans,trans-muconaldehyde inhibited NADPH-cytochrome c reductase. Crotonaldehyde was a less effective inhibitor of this enzyme. Propionaldehyde, a saturated aldehyde, had no effect on NADPH-cytochrome c reductase activity. Time course experiments with acrolein over a period of 5–45 min suggest that the loss of NADPH-cytochrome c reductase activity is non-linear. The addition of reduced glutathione protected against the inhibition of reductase activity by acrolein. Formation of these aldehydes and their subsequent inhibition of these enzymes may have important consequences in xenobiotic metabolism.