REGULATION OF STEROID-PRODUCTION IN OVARIAN STROMAL TISSUE FROM 5-WEEK-OLD TO 8-WEEK-OLD PULLETS AND LAYING HENS

Studies were conducted to evaluate the regulation of steroid productio n in dispersed cells from ovarian stromal tissue from 5- to 8-week-old -pullets (IM cells) and laying hens (MAT cells). Short-term incubation of IM and MAT cells with ovine (o) LH resulted in a dose-dependent in crease in progesterone, androstenedione and oestradiol production; pro gesterone production was greater in MAT cells than in IM cells (P < 0. 05) in response to 2-200 ng oLH ml(-1), whereas androstenedione and oe stradiol Production was greater in MAT cells following treatment with 20 and 200 ng oLH ml(-1) (P < 0.05). In both cell populations the cycl ic adenosine monophosphate (cAMP) analogue, 8-bromo-cAMP (1 and 10 mmo l l(-1)) stimulated progesterone and androstenedione production, where as oLH (200 ng ml(-1)) and forskolin (1-10 mu mol l(-1)) promoted cAMP accumulation (P < 0.05 compared with basal values). However, treatmen t with the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA), did not alter basal or oLH-stimulated cAMP accumulation or pro gesterone production in either IM or MAT cells (P > 0.10). PMA did, ho wever, inhibit agonist-induced androstenedione production (P < 0.05); co-treatment with the calcium ionophore A23187 potentiated this inhibi tory effect. Finally, treatment with transforming growth factor-alpha (TGF-alpha; 1.8-18 pmol l(-1)) did not affect basal or oLH-stimulated progesterone or androstenedione production by IM cells, MAT cells, the ca cells from 6-8 mm follicles or theca cells from the second largest (F2) follicle (P > 0.10). We conclude that LH-stimulated steroid produ ction is greater in MAT cells than in IM cells; production of steroids at both stages occurs, at least in part, via the adenylyl cyclase/cyc lic AMP second messenger pathway. However, we propose that activation of protein kinase C can inhibit agonist-induced cytochrome P450 17 alp ha-hydroxylase, but not cytochrome P450 cholesterol side-chain cleavag e, activity in stromal cells. Finally, steroidogenesis in stromal tiss ue from 5- to 8-week-old pullet and laying hen ovaries is regulated by hormonal and cellular mechanisms most comparable to those that modula te steroidogenesis in theca cells from 6- to 8-mm and F2 follicles.