Abstract: 446

INHIBITION BY CANTHARIDIN OF STEROIDOGENIC ACUTE REGULATORY PROTEIN EXPRESSION DURING FOLLICULAR DEVELOPMENT IN THE RAT OVARY.

PS Li^{1 *}, LM Huang¹ , TJ Huang¹
Department of Physiology, College of Medicine, National Cheng Kung University, Tainan, Taiwan ¹

Cantharidin (CAN), a natural toxicant of several species of blister beetles, is reputed to possess aphrodisiac and abortifacient properties in humans. The aphrodisiac legend stems from CAN's ability to cause vascular congestion and inflammation of the genitourinary tract, a sensation that may be interpreted as enhanced sexuality by some. It has been reported that CAN can inhibit testosterone production from rat Leydig cells. In the present study, we evaluated the effect of CAN on the protein levels of steroidogenic acute regulatory protein (StAR), the rate-limiting step in steroidogenesis, in the rat ovary. Pregnant mare serum gonadotropin (PMSG; 10 IU) and CAN (1 mg/kg BW) were administered at 1000 h to 24-day-old rats, and 48 h later the luteinizing hormone (LH) surge was stimulated by human chorionic gonadotropin (hCG; 5 IU). At 48, 60, 72, and 84 h after PMSG administration, protein extracts of whole ovarian tissue were prepared and StAR products were determined by Western blot analysis. Control animals were not treated with the CAN. Before PMSG administration, StAR protein levels were barely detectable. A significant rise in StAR protein was observed at 48 h after PMSG administration. Exogenous hCG stimulation elicited a peak in StAR protein levels, which reached maximal values within 12 h of hCG administration. Treatment with CAN decreased the level of StAR protein at 48 h after PMSG administration or at 24 h and 36 h after hCG administration. Treatment of preovulatory follicles dissected from ovaries of PMSG-treated immature rats with increasing concentrations (0.01-1 g/ml) of CAN also inhibited both StAR protein level and progesterone production in response to LH and cAMP analog stimulation. These observations indicate that during hormone induced follicular development in the rat, expression of the ovarian StAR can be suppressed by CAN and, thus, suggest that ingestion of CAN can decrease ovarian function. This inhibitory effect may be accounted for, at least in part, by the suppression of StAR protein synthesis.

    This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.