Ovarian ∆5-3β-hydroxysteroid dehydrogenase in aging rats

Ovaries of rats 1, 2, 4, and 18 months old revealed significant delta-5-3-beta-hydroxysteroid dehydrogenase (3beta-OHSD) activity when dehydroepiandrosterone (DHA), pregnenolone, and 16-dehydropregnenolone served as substrates. No enzyme activity was evident in ovaries 4 and 18 months of age when the substrates 17alpha-hydroxypregnenolone, pregnenolone sulfate, and dehydroepiandrosterone sulfate were used. A marked increase in enzyme activity occurred in the granulosae of mature vesicular follicles at 18 months of age. DHA, pregnenolone, and 16-dehydropregnenolone provided similar activities. On the other hand, interstitial enzyme activity exhibited an aging decline with DHA and 16-dehydropregnenolone but increased with pregnenolone. Corpora lutea were less evident in aging ovaries but did exhibit strong 3beta-OHSD activity when DHA was used. Pregnenolone use by corpora lutea was sharply increased in aging rats but no change occurred with 16-dehydropregnenolone. Thus aging was associated with changes in 3beta-OHSD distribution and use of steroid substrate; a change in function is suggested.