Hormonal competence of porcine cystic ovaries

The pathological and biochemical features of porcine cystic ovarian disease in animals identified at slaughter was characterized with particular regard to steroidogenic function. Serum and ovarian follicular fluid were analyzed for ten steroid hormones by a multiple simultaneous radioimmunoassay technique. The steroids measured were pregnenolone, progesterone, 20$\alpha$-dihydroprogesterone, 17$\alpha$-hydroxyprogesterone, androstenedione, 5$\alpha$-dihydrotestosterone, dehydroepiandrosterone, testosterone, estrone, and estradiol. Steroidogenic activity of ovarian tissue was investigated by radioenzymatic assays of 3$\beta$-hydroxysteroid dehydrogenase/isomerase (3$\beta$-OHSD), 17$\alpha$-hydroxylase, and 17, 20-lyase enzymes, as well as immunocytochemical analysis using a highly specific antibody to porcine cytochrome P-450$\sb{17\alpha}$ hydroxylase (P-450$\sb{17\alpha}$; XVIIA1). All the follicular fluid steroids measured except 5$\alpha$-dihydrotestosterone increased in concentration up to the late preovulatory stage of normal ovarian cycle. While levels of other steroids declined significantly at ovulation, 20$\alpha$-dihydroprogesterone concentration was elevated at this stage. In general, progestins, especially progesterone, accumulated excessively in cysts compared to normal follicles. Progesterone level increased with luteinization of cystic follicles to as much as 10 times those found in large normal preovulatory follicles. In contrast, the concentration of androgens and estrogens were barely detectable. Plasma levels of steroids in animals with cystic ovaries were generally in the range of that found in normal animals in the luteal stage of the estrous cycle. Kinetic analysis of radioenzymatic assays showed 3$\beta$-hydroxysteroid dehydrogenase/$\Delta\sp4$-$\Delta\sp5$ isomerase activity (Vmax) to be similar in cystic and corpora lutea tissues and 8 times higher than that found in normal preovulatory follicles. In contrast, the formation of either corpora lutea or luteinized cysts led to a profound decline (12- to 15-fold) in 17$\alpha$-hydroxylase and 17,20-lyase activities as compared to normal preovulatory follicles. Moreover, the P-450$\sb{17\alpha}$ enzyme protein, which is localized specifically in the theca interna cells of normal follicles, was not immunocytochemically detectable in luteinized cystic follicles. These studies characterized the steroid changes that occur with the formation of cystic follicles and demonstrate functional similarities with normal corpora lutea. Results in this study therefore indicate a pathologically increased activity of the 3$\beta$-OHSD enzyme, and suppression of cytochrome P-450$\sb{17\alpha}$ expression in porcine cystic ovaries