Steroidogenic enzyme activities in rat polycystic ovaries

Abstract

Ovaries containing multiple follicular cysts occur in a variety of anovulatory conditions. A macrocystic condition occurs spontaneously in rats following a single injection of estradiol valerate. The ovaries are small, and exhibit scant stromal tissue, few healthy follicles, and numerous large cystic and precystic follicles. We have also generated a microcystic condition by means of subcutaneous estradiol-containing silastic implants. These ovaries are large, and exhibit a stroma of hypertrophied lipid-filled cells, and numerous small cysts encircled by hypertrophied thecal cells. The macrocystic condition is associated with a uniformly attenuated plasma luteinizing hormone (LH) pattern, whereas large LH episodes characterize the microcystic condition. The marked dissimilarities between these two methods suggest that there may be corresponding differences in ovarian steroidogenic activity. We have measured the activity of enzymes involved in progestin and androgen biosynthesis in the two types of multicystic ovaries before and after LH – human chorionic gonadotropin (hCG) stimulation. Control ovaries were obtained at late proestrus from age-matched cycling animals. Radiometric enzyme assays for 3β-hydroxysteroid dehydrogenase (3β-HSD), 20α-hydroxysteroid dehydrogenase (20α-HSD), C17,20-lyase (lyase), and aromatase were conducted on the microsomal fraction of ovarian homogenates. 3β-HSD activity was reduced by > 50% in both types of cystic ovaries compared with controls. There was a slight elevation in the 3β-HSD activity of macrocystic ovaries in response to hCG. 20α-HSD activity was similar in controls and macrocystic ovaries but significantly lower (< 20% of control) in the microcystic ovaries. Lyase and aromatase activities were undetectable in cystic ovaries. Although these results are consistent with the morphology and plasma LH patterns characterizing the macrocystic condition, the microcystic ovary presents an unexpected paradox. These results underscore the complexity and multidimensional nature of cystic ovarian disease.Key words: steroidogenic activity, ovary, polycystic.