Specific receptor-mediated stimulation of progesterone secretion and cGMP accumulation by rat atrial natriuretic factor in cultured human granulosa-lutein (G-L) cells.

The effect of rat atrial natriuretic factor (ANFIV102-126) on the regulation of steroidogenesis in human G-L cells have been studied in vitro. The treatment of cells with ANF (1 X 10(-8)M) resulted in a 3- to 4-fold increase in progesterone secretion compared to the controls. ANF in combination with LH (200 ng/ml) increased progesterone secretion more than six-fold over controls. Concomitantly, ANF stimulated the accumulation of cGMP 30-fold, whereas the level of cAMP was either unchanged or fell slightly (10-15%). Mono[125I]-iodo-ANF bound to G-L cell surface specific receptors with a Kd of 1.8 X 10(-10)M at a density (Bmax) of 160,000-190,000 sites/cell. The binding of [125I]-iodo-ANF was competed by unlabeled ANF in a dose-dependent manner, and hormones unrelated to ANF, such as angiotensins, ACTH or LH, were unable to compete with [125I]-iodo-ANF. The results indicate that ANF can stimulate progesterone secretion and cGMP accumulation in ovarian G-L cells without affecting the level of cAMP and that the stimulatory effects of ANF on G-L cell steroidogenesis may proceed via mechanism(s) involving an intracellular messenger other than cAMP.