Stimulation of drug-metabolizing enzymes by nitrous oxide in the rat.

Wistar male rats were subchronically (150 h continuously) or chronically (5 h daily for 15 days) exposed to a 50% nitrous oxide/oxygen mixture. As an index of enzyme induction liver N-demethylase and benzo(a)pyrene-hydroxylase activities, serum gamma-glutamyltranspeptidase activity, urinary d-glucaric acid and pentobarbital sleeping time were evaluated in comparison with a control group. No effect was observed after subchronic exposure to the anaesthetic gas. Chronic exposure, on the contrary, decreased pentobarbital sleeping time, increased urinary d-glucaric acid, liver N-demethylase and serum gamma-glutamyltranspeptidase activities. No increase of liver benzo(a)pyrene-hydroxylase was observed. Chronic nitrous oxide exposure under appropriate conditions can modify some enzymes, metabolizing drugs and xenobiotic compounds.