Inhibition of testosterone metabolism in the brain and cloacal gland of the quail by specific inhibitors and antihormones.

The effects of antioestrogens, antiandrogens and of various inhibitors of testosterone metabolism on testosterone metabolism in the quail hypothalamus and cloacal gland were studied by an in-vitro radioenzymatic assay. It was found that antioestrogens and antiandrogens generally had little or no effect on aromatase and 5 alpha- and 5 beta-reductases of testosterone, except when used at very high doses. The 5 alpha-reductase inhibitor, 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one, inhibited both 5 alpha- and 5 beta-dihydrotestosterone production without markedly affecting aromatase activity. Surprisingly, the aromatase inhibitor, 1,4,6-androstatriene-3,17-dione, inhibited not only the production of oestradiol but also that of 5 beta-dihydrotestosterone and, to a lesser extent, 5 alpha-dihydrotestosterone. These unexpected properties should be taken into account when interpreting the results of in-vivo experiments using these compounds.