Comparison of induced corpora lutea from prepuberal gilts and spontaneous corpora lutea from mature gilts: hydroxysteroid dehydrogenase activity.

The activity of hydroxysteroid dehydrogenases was histochemically quantified in corpora lutea (CL) from prepuberal gilts induced to ovulate and mature gilts. Prepuberal (P) gilts, 120 to 130 d of age were induced to ovulate with 1,500 IU pregnant mare serum gonadotropin (PMSG) followed 72 h later by 500 IU human chorionic gonadotropin (hCG). Three P gilts and three mature (M) gilts each were ovariectomized on d 10, 14, 18, 22 and 26 (d 0 = day of hCG for P gilts and onset of estrus for M gilts). Gilts ovariectomized on d 14, 18, 22 and 26 were hysterectomized on d 6 to ensure luteal maintenance. At the time of ovariectomy, CL were frozen in liquid nitrogen and then stored at -80 C until analysis. Cryostat sections (12 microns) were histochemically analyzed for delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta OHSD), 17 alpha-hydroxysteroid dehydrogenase (17 alpha OHSD) and 20 alpha-hydroxysteroid dehydrogenase (20 alpha OHSD). The intensity of staining (greater enzyme activity resulted in darker staining) was quantified using a Zeiss SF microscope integrated with a Zonax photometer, which measured the percentage of light transmitted through a given area (22,500 microns 2) of the tissue section. Data were subjected to analysis of variance using the general linear models procedure of Statistical Analysis System (SAS). The 3 beta OHSD activity did not change over days, but the mean activity (throughout all days) in the P gilts (32.6 +/- 1.8) tended (P less than .08) to be elevated above that of M gilts (27.9 +/- 1.7).(ABSTRACT TRUNCATED AT 250 WORDS)