title: The development of hepatic drug-metabolizing enzyme activity in the neonatal calf and its effect on drug disposition.
abstract: Mixed function oxidase and UDP-glucuronyltransferase activity was measured in liver microsomal preparations from 1-, 7-, and 42-day-old, male, Holstein calves. Liver samples were obtained by a surgical biopsy procedure that allowed for multiple samples to be taken from a single individual. Microsomal protein content doubled between 7 and 42 days of age and reached adult levels during this time. Cytochrome P-450 content increased 2-fold during the first week and remained constant thereafter. NADPH-cytochrome c reductase activity doubled during the first week, but then returned to its initial level by 42 days of age. UDP-glucuronyltransferase activity was well developed at 1 day of age and reached adult levels by 7 days of age. Mixed function oxidase activity was less well developed; activities at 1 day of age were only 17-50% of those at 42 days of age for O-deethylation, O- and N-demethylation, and aryl hydrocarbon hydroxylation. Development of hepatic drug-metabolizing activity was discussed in relation to the age-related increase in the rate of elimination of the antibacterial compound trimethoprim.
mesh_terms: D015660:7-Alkoxycoumarin O-Dealkylase; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001579:Benzopyrene Hydroxylase / Q000378:metabolism; D002417:Cattle; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D010090:Oxidoreductases, O-Demethylating / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism; D004364:Pharmaceutical Preparations / Q000378:metabolism*
chemical_list: D004364:Pharmaceutical Preparations; D003577:Cytochrome P-450 Enzyme System; C026048:4-nitroanisole O-demethylase; D006899:Mixed Function Oxygenases; D010090:Oxidoreductases, O-Demethylating; D010105:Oxygenases; D015660:7-Alkoxycoumarin O-Dealkylase; D001579:Benzopyrene Hydroxylase; C019781:benzphetamine N-demethylase; D010089:Oxidoreductases, N-Demethylating; D009251:NADPH-Ferrihemoprotein Reductase; D014453:Glucuronosyltransferase