7-Ethoxycoumarin metabolism in hepatocytes from pre- and postpubescent male rats.

Marked changes in rates of drug metabolism occur during adolescence; however, biochemical events underlying alterations in drug metabolism in whole hepatocytes during this period of development are not well established. Accordingly, metabolism of 7-ethoxycoumarin, a model substrate for mixed-function oxidation, was studied in hepatocytes isolated from prepubescent and postpubescent male rats. Rates of 7-ethoxycoumarin O-deethylation increased 2.4-fold from 65 to 154 pmol/10(6) cells/min in intact hepatocytes during the narrow period of adolescence. In contrast, microsomal 7-ethoxycoumarin O-deethylase was the same in preparations from the two groups of animals. 7-Hydroxycoumarin glucuronide production in hepatocytes increased 2-fold and sulfate formation increased 16-fold across puberty. The results indicate that increases in drug metabolism, particularly sulfate conjugation, are mediated by biochemical events in addition to increases in total amounts and specific activities of hepatic drug-metabolizing enzymes.