Ovarian Steroid Dehydrogenase Histochemistry and Circulating Progesterone in Aged Golden Hamsters During the Estrous Cycle and Pregnancy1

Abstract

The histochemical activity of the enzymes Δ5-3β-hydroxysteroid dehydrogenase (3βHSD) and 17β-hydroxysteroid dehydrogenase (17βHSD) was studied in the ovaries of aged golden hamsters. These enzymes are operative in progesterone synthesis (3βHSD) and 17β-estradiol-estrone interconversion (17βHSD). Blood levels of circulating progesterone were determined in the same animals. Data from the old animals were compared to measurements of these same parameters from young hamsters. The pattern of 3βHSD activity was similar in young and old animals, appearing in follicles and corpora lutea at appropriate times of their function and in interstitium at all times. The 17βHSD activity was only found in follicular granulosa cells during the cycle and the first half of pregnancy of young and old animals, but was also found in corpora lutea in later pregnancy. The ovaries from old animals differed from those from young animals mainly in the degree of development of various components. There was much individual variability, but often old ones had fewer large follicles, fewer ovulations, and more corpora lutea atretica. Interstitium with 3βHSD was less abundant and replaced by pigment or condensed inactive stroma. Circulating progesterone was not significantly lower than normal in old hamsters and on certain days some even had exceptionally high levels compared to young. Old hamsters carried fetuses to term but did not deliver them, apparently because their corpora lutea continued to secrete progesterone. The fact that many old hamsters resorb conceptuses or fail to have implantations does not appear to be primarily related to lack of progesterone or deficiency of ovarian steroid dehydrogenases.