2-Hydroxyestradiol modulates a facilitative action of catecholamines on porcine granulosa cells

Recent studies have disclosed a novel intraovarian paracrine system whereby catecholestrogens [e.g. 2-hydroxyestradiol (2-OH-E2)], synthesized locally from estradiol (E2) can stimulate progesterone secretion by granulosa cells (GC). Since these studies suggested that effects of 2-OH-E2 were discrete from those of E2, the present studies were undertaken to determine if the effects of 2-OH-E2 could be mediated through or interact with the catecholamine response system of GC. First, the effects of 2-OH-E2 were compared with those of E2 and epinephrine (EPI) using undifferentiated porcine GC. After 4 days of treatment, saturating concentrations of EPI (1 microgram/ml), 2-OH-E2 (4 micrograms/ml), and E2 (1 microgram/ml) stimulated progesterone production per cell 2-, 9-, and 10-fold, respectively. Saturating doses of EPI plus 2-OH-E2 or EPI plus E2 caused further significant increases in progesterone production above the effects of any single treatment, and the effects of EPI plus 2-OH-E2 were significantly greater than that of EPI plus E2. Isoproterenol mimicked the effect of EPI. Neither propranolol (a beta-antagonist) nor phentolamine (an alpha-antagonist) blocked the effects of 2-OH-E2, suggesting that effects of 2-OH-E2 were not mediated through alpha- or beta-adrenergic receptors. Collectively, these data suggest that 2-OH-E2, beta-adrenergic agonists, and E2 use separate response systems. To further evaluate the interaction between catecholamines and 2-OH-E2, GC were treated with increasing doses of 2-OH-E2 with or without EPI or isoproterenol. EPI and isoproterenol caused a synergistic increase in progesterone production above that induced by all doses of 2-OH-E2 along (average 3.8 +/- 0.7- and 3.2 +/- 0.4-fold enhancement for EPI and isoproterenol, respectively). This synergistic effect was blocked with addition of propranolol, indicating a beta-adrenergic mediation for the catecholamine portion of this effect. Studies using the catechol-O-methyltransferase inhibitor, U-0521, and the O-methyl derivative of EPI, metanephrine, suggested that catechol-O-methyltransferase present in GC dramatically reduces the potency of EPI, but is not involved in the synergism between EPI and 2-OH-E2. In conclusion, 2-OH-E2 is a more efficacious stimulator of progesterone secretion than catecholamines and synergizes with beta-adrenergic agonists to further stimulate progesterone production by GC. The mechanism by which catecholamines and 2-OH-E2 interact within GC is unknown.4+owever, this catecholamine/2-OH-E2 interaction