title: Comparison of rate of hepatic metabolism in vitro and half-life for antipyrine in vivo in three species.
abstract: 1. A radiometric assay for the total metabolism of antipyrine in vitro by hepatic microsomal preparations has been developed. 2. Apparent Km and V values for the process were determined in rats, rabbits and in a marsupial (the quokka; Setomix brachyurus). Km values were similar in rats and rabbits (3.5 and 5 mM respectively) but were somewhat lower in quokkas (1.4--1.5 mM). Estimates of V ranged from 49--64 nmol/mg microsomal protein/10 min and were similar in all three species. Pretreatment of rabbits with phenobarbitone significantly increased V without change in Km. 3. Studies in individual rabbits and quokkas showed a good correlation between rate of hepatic microsomal metabolism of antipyrine in vitro and its half-life in vivo.
mesh_terms: D000818:Animals; D000983:Antipyrine / Q000097:blood / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003579:Cytochrome Reductases / Q000378:metabolism; D006207:Half-Life; D007700:Kinetics; D007614:Macropodidae; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D013045:Species Specificity
chemical_list: D003577:Cytochrome P-450 Enzyme System; D003579:Cytochrome Reductases; D000983:Antipyrine; D010634:Phenobarbital