DISCONTINUOUS VARIATION IN HEPATIC URIDINE-DIPHOSPHATE GLUCURONYLTRANSFERASE TOWARD ANDROSTERONE IN WISTAR RATS - REGULATORY FACTOR FOR INVIVO METABOLISM OF ANDROSTERONE

Male and female Wistar rats showed discontinuous variation in hepatic microsomal UDP-glucuronyltransferase activities toward androsterone but not toward testosterone. In contrast, Sprague-Dawley rats. Hartley guinea pigs and CF#1 mice did not exhibit such diversity. Microsomes with a high level of transferase activity toward androsterone (HG) and microsomes with a low level of transferase activity (LG) were found approximately in the ratio 5:4 in male and female Wistar rats, the HG to LG specific activity ratio being about 9. In the presence of Triton X-100, the enzyme activity was stimulated maximally (5-fold) and the HG to LG specific activity ratio increased to 16. Kinetic studies revealed that the transferase had a much lower affinity toward androsterone in the LG microsomes than in the HG micro-somes. These results confirm the view that hepatic UDP-glucuronyltransferase is principally responsible for the large variations in the metabolism in vivo of androsterone and testosterone in female Wistar rats. © 1979.