EFFECTS OF METABOLIC HORMONES AND GROWTH-FACTORS ON FORSKOLIN AND DIBUTYRYL ADENOSINE 3',5'-CYCLIC-MONOPHOSPHATE INDUCED STEROIDOGENIC RESPONSES BY PORCINE GRANULOSA-CELLS IN-VITRO

The present experiments were conducted to examine the influence of met abolic hormones and growth factors on progesterone and estradiol secre tion by porcine granulosa cells in culture and to determine the possib le site(s) of action of these agents on steroidogenesis. Porcine granu losa cells, obtained from medium-sized (4-6 mm) nonatretic follicles o f prepubertal gilts slaughtered at a commercial abattoir, were culture d at a density of 2 x 10(6) viable cells well(-1) in serum-free Eagle' s Minumum Essential Medium for 72 h with 0, 10 or 100 ng mL(-1) of GH, insulin or ICE-I or ICE-II. At 72 h, each treatment group was divided into three subgroups, one subgroup remained untreated (basal) while e ither 25 mu M FK or 3 mM dbcAMP was added to the other two subgroups. Additionally, androstenedione (10(-7) M) was provided to all cultures as a substrate for estradiol biosynthesis. Media were collected at 96 h for determination of progesterone and estradiol content. Both ICE-I and ICE-II increased (P < 0.01) basal progesterone and estradiol secre tion and enhanced the FK- and dbcAMP-induced stimulation of progestero ne and estradiol secretion (P < 0.01). Insulin, at 100 ng mL(-1), had a modest but significant positive effect on both FK- and dbcAMP-stimul ated steroidogenic responses. In contrast, GH inhibited basal, FK- and dbcAMP-induced progesterone and estradiol production. Based on the st imulatory effects of both IGFs above those seen with dbcAMP alone and the inhibitory effects of GH in the face of dbcAMP stimulation, we con clude that their effects are likely mediated by non-cAMP dependent pat hways.