Evidence that the same structural gene encodes testicular and adrenal 3 beta-hydroxysteroid dehydrogenase-isomerase.

Thermostability of 3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta HSD) activity was examined in testes and adrenal glands from several inbred lines and feral mice. A thermolabile variant of 3 beta HSD was detected in the feral Brno mice. The thermostability (t1/2) of 3 beta HSD was approximately 7 min for both testes and adrenal glands from C57BL/6J mice, compared with 4 min for both tissues from Brno mice. Comparison of testicular and adrenal 3 beta HSD thermostability in six kinds of mice indicated that the t1/2 of 3 beta HSD was correlated in the two tissues and could be classified into two distinct types, thermolabile and thermostable. In contrast, quantitative variants in 3 beta HSD activity were not correlated in the two tissues. These data are consistent with the hypothesis that testicular and adrenal 3 beta HSD is encoded by the same structural gene but that expression of 3 beta HSD activity is independently controlled in testes and adrenal glands.