RESUMEN
Main function of corpus luteum is progesterone synthesis that is significantly accompanied with an increase in levels of mRNA encoding of steroidogenic enzymes known as luteal markers. This study was designed to evaluate effects of lithium chloride on the release of steroid hormones and steroidogenic enzymes in gonadotropin-stimulated rats. Immature 23 days old Wistar rats were divided into 10 groups; each group comprised of 8 rats, and induced with single injection of pregnant mare's serum gonadotrophin [PMSG] and followed by single injection of human chorionic gonadotropin [hCG]. Then, rats were given lithium chloride [LiCl] or saline at 12 hours post-hCG injection. Ovaries were collected in 4-hour interval from 8-24 hour post-hCG injection. Expression pattern of steroidogenic acute regulatory protein [StAR], side-chain cleavage cytochrome P450 [P450scc] and 3beta-hydroxysteroid dehydrogenase [3beta-HSD] genes were determined by semi-quantitative RT-PCR. In addition, serum levels of progesterone and 17beta-estradiol were measured by ELISA. Our results showed that hCG stimulation of progesterone was markedly diminished and transcript levels of key steroidogenic enzymes were altered in the hormone-stimulated rats following LiCl treatment. These results suggest that critical steps in the function of corpus luteum are disrupted by lithium. It is concluded that LiCl is an effective factor for suppressing of steroid genes expression