Adrenergic regulation of ovarian androgen biosynthesis is mediated via beta 2-adrenergic theca-interstitial cell...

Acting alone or in concert with pituitary gonadotropins, catecholamines have recently been shown to enhance androgen production by ovarian theca-interstitial cells. It is the objective of the in vitro studies reported herein to further characterize this catecholaminergic activity as well as to type and subtype the putative adrenergic recognition sites mediating this phenomenon. Treatment of collagenase-processed whole ovarian dispersates or highly enriched (greater than 90%) theca-interstitial cells from immature rats with norepinephrine (10(-6) M) resulted in a 2.0-fold increment in the accumulation of androsterone (3 alpha-hydroxy-5 alpha-androstane-17-one), the main androgenic steroid identified in culture medium by HPLC. Qualitatively similar stimulation was obtained using beta (isoproterenol)- but not alpha (methoxamine)-selective adrenergic agonists. Moreover, combined treatment with both norepinephrine (10(-6) M) and hCG (1 ng/ml) unmasked a synergistic interaction subject to stereospecific blockade by beta (propranolol)- but not alpha (phentolamine)-selective adrenergic antagonists. Further probing with subtype-selective adrenergic ligands revealed terbutaline (a beta 2-selective agonist) to enhance androgen biosynthesis, with dobutamine (a beta 1-selective agonist) having little or no effect. Moreover, a beta 2 (ICI-118406)- but not a beta 1 (ICI-89406)-selective adrenergic antagonist yielded dose-dependent inhibition of the isoproterenol effect. Unaccounted for by either enhanced cellular growth or an alteration of the overall steroidogenic pattern, catecholaminergically stimulated androgen biosynthesis proved time and dose dependent but independent of the hCG dose (0.1-10 ng/ml) employed. Binding of [125I]iodocyanopindolol to highly enriched theca-interstitial cells proved stereoselective and saturable, displaying a single class (Hill coefficient = 0.96 +/- 0.01) of high affinity (Kd = 5.6 X 10(-11) M), low capacity (1219 +/- 317 sites/cell) binding sites. The rank order of competitive potencies of selective adrenergic ligands (beta 2 greater than beta 1 greater than alpha), was consistent with a beta 2-adrenergic receptor subtype. Taken together, these findings suggest that catecholaminergic stimulation of ovarian androgen biosynthesis is mediated via beta 2-adrenergic recognition sites, the role of which may now be studied.