Abstract: 238

EFFECTS OF DIGOXIN, DIGITOXIN, AND OUABAIN ON PROGESTERONE RELEASE BY RAT GRANULOSA CELLS.

JJ Chen^{1 *}, SC Tsai^{1 *}, JL Wang¹ , YC Chiao^{1 *}, H Lin¹ , SW Wang^{2 *}, EJ Chien¹ , PS Wang^{1 *}
Dept. Physiol., Natl. Yang-Ming Univ., Taipei, Taiwan, ROC ¹
Dept. Physiol., Chang Gung Univ., Taoyuan, Taiwan, ROC ²

Digoxin and digitoxin are two compounds of digitalis, which have been used clinically in treatment of congestive heart disease via an inhibition of Na⁺,K⁺-ATPase activity. However, the endocrine functions of digitalis are still unclear. In the present study, the effects of digoxin, digitoxin, and ouabain (a selective Na⁺,K⁺-ATPase inhibitor) on the production of progesterone (P) were examined. Ovarian granulosa cells were isolated from immature female rats treated with pregnant mare serum gonadotropin and incubated in medium DMEM/F12 with 10% fetal calf serum. After preincubation for 48 h, rat granulosa cells (1 × 10⁵ cells/well) were incubated with 0.5 ml fresh medium 199 containing 0.3% bovine serum albumin and different doses of digoxin, digitoxin, or ouabain in the presence or absence of human chorionic gonadotropin (hCG), forskolin (an adenylyl cyclase activator), 8-bromo-adenosine 3':5'-cyclic momophosphate (8-Br-cAMP, a membrane-permeable analog of cAMP) or steroidogenic precursors including 25-hydroxy-cholesterol (25-OH-C) and pregnenolone. The concentration of medium P was measured by RIA. Either digoxin or digitoxin, but not ouabain, decreased the basal and hCG-stimulated P release by rat granulosa cells. Administration of forskolin or 8-Br-cAMP did not reverse the inhibition of digoxin and digitoxin on P release. Furthermore, pregnenolone, but not 25-OH-C, prevented the inhibition of digoxin and digitoxin on P release. These results suggest that digoxin and digitoxin decrease the progesterone release by rat granulosa cells via a Na⁺, K⁺-ATPase-independent mechanism involving the inhibition of cAMP and P450_scc (desmolase) activities.

    This abstract is being presented on Monday, August 2 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.