Regulation of steroid production in ovarian stromal tissue from 5- to 8-week-old pullets and laying hens

Studies were conducted to evaluate the regulation of steroid production 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 increase in progesterone, androstenedione and oestradiol production; progesterone 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 oestradiol production was greater in MAT cells following treatment with 20 and 200 ng oLH ml^-1 (P < 0.05). In both cell populations the cyclic adenosine monophosphate (cAMP) analogue, 8-bromo-cAMP (1 and 10 mmol l^-1) stimulated progesterone and androstenedione production, whereas oLH (200 ng ml^-1) and forskolin (1-10 μmol l^-1) promoted cAMP accumulation (P < 0.05 compared with basal values). However, treatment with the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA), did not alter basal or oLH-stimulated cAMP accumulation or progesterone production in either IM or MAT cells (P > 0.10). PMA did, however, inhibit agonist-induced androstenedione production (P < 0.05); co-treatment with the calcium ionophore A23187 potentiated this inhibitory effect. Finally, treatment with transforming growth factor-α (TGF-α; 1.8-18 pmol l^-1) did not affect basal or oLH-stimulated progesterone or androstenedione production by IM cells, MAT cells, theca cells from 6-8 mm follicles or theca cells from the second largest (F2) follicle (P > 0.10). We conclude that LH-stimulated steroid production is greater in MAT cells than in IM cells; production of steroids at both stages occurs, at least in part, via the adenylyl cyclase/cyclic AMP second messenger pathway. However, we propose that activation of protein kinase C can inhibit agonist-induced cytochrome P450 17α-hydroxylase, but not cytochrome P450 cholesterol side-chain cleavage, activity in stromal cells. Finally, steroidogenesis in stromal tissue from 5- to 8-week-old pullet and laying hen ovaries is regulated by hormonal and cellular mechanisms most comparable to those that modulate steroidogenesis in theca cells from 6- to 8-mm and F2 follicles.