In vitro uptake and metabolism of testosterone by goldfish, Carassius auratus, mesenteric adipose tissue

Mesenteric adipose tissue was removed from adult goldfish, Carassius auratus, and incubated in vitro with (1alpha,2alpha)-3[H]testosterone (T). Total radioactivity in the medium decreased and tissue total radioactivity increased in a time-dependent fashion between 1 and 6 h of incubation with maximum uptake occurring between 4 and 6 h. After ether extraction and thin layer chromatography the amount of radioactivity comigrating with authentic T standard decreased over time in both medium and tissue samples. Radioactivity in the aqueous fraction remaining after ether extraction increased in a time-dependent manner, suggesting the presence of water-soluble conjugated steroids. Acid hydrolysis of the aqueous fraction yielded radioactivity that principally comigrated with T standard following a second ether extraction and TLC, along with a small, unidentified peak of poorly migrating radioactivity. Aromatization of T was assessed after charcoal stripping samples and measuring radioactivity remaining in the form of 3H(2)O. Small but significant amounts of 3H(2)O were present in both incubation medium and tissue samples. Incubation with the aromatase inhibitor 4-androsten-4-ol-3,17-dione acetate (ATD) decreased the formation of 3H(2)O in a dose-dependent manner. These results suggest that goldfish mesenteric adipose tissue is capable of converting T to several metabolites including water-soluble conjugates and estrogen.