[Hexobarbital-oxidation in vivo and in vitro in rats after phenobarbital-pretreatment or after portacaval anastomosis (author's transl)].

Male rats were pretreated with phenobarbital for 5 days or received portacaval anastomosis 3 weeks before. Hexobarbital was applicated intravenously and hexobarbital plasma concentrations were followed up gaschromatographically in arterial blood samples. Hexobarbital clearance was calculated from the plasma concentration curve versus time. Liver microsomes were prepared and cytochrome P 450 and the hexobarbital oxidation rate was determined. After portacaval shunt the animals showed a small liver, a reduced cytochrome P 450 and diminished hexobarbital oxidation rate. Hexobarbital clearance in vivo was reduced, too. After phenobarbital pretreatment liver weight increased and cytochrome P 450 and hexobarbital oxidation rate were distinctly enhanced. The hexobarbital clearance in vivo were increased. Since the plot of hexobarbital clearance in vivo versus cytochrome P 450 or versus hexobarbital oxidation rate in vitro gave a good correlation, it is concluded that hexobarbital clearance in vivo may be a good estimate for hepatic cytochrome P 450 and hepatic hexobarbital oxidation rate.