Demonstration of functional heterogeneity of hepatic uridine diphosphate glucuronosyltransferase activities after administration of 3-methylcholanthrene and phenobarbital to rats

After the administration of 3-methylcholanthrene to adult male rats, activities of hepatic UDP-glucuronosyltransferase towards six from a group of 12 substrates were stimulated by 250-350%. Activities towards the remaining six substrates were unaffected. Conversely, after phenobarbital administration, activities formerly stimulated by 3-methylcholanthrene remained unchanged, and the other six activities were stimulated by 160-280%. The relationship of these two groups of transferase activities to other evidence suggesting the same heterogeneity of the enzyme is discussed.