Résumé
The regulation of secretion of chorionic gonadotropin in primates has been studied using both in vivo and in vitro models. In vivo studies using the pregnant bonnet monkey revealed that at the doses tested, the administration of progesterone or estradiol 17β in combination or alone did not result in any appreciable change in the duration or magnitude of serum chorionic gonadotropin levels. However, administration of lutropin-releasing hormone by intravenous route resulted in significant increase in chorionic gonadotropin levels within 30–60 min and the extent of stimulation seemed to depend on the state of pregnancy. For in vitro studies, explants or cells prepared from first trimester human placenta has been used. The functional integrity of these cells has been established by demonstrating the binding of [125I]- labelled human chorionic gonadotropin antibody to the cells as well as the synthesis of [3H]- labelled human chorionic gonadotropin. In vitro studies using the cells revealed that addition of lutropin-releasing hormone caused a significant increase in chorionic gonadotropin and estradiol 17 β secreted into the medium. Thus both in vivo and in vitro results suggest that lutropin-releasing hormone could be one of the factors involved in regulation of chorionic gonadotropin secretion in primates.
Résumé
Administration of human chorionic gonadotropin to pregnant bonnet monkeys (Macaca radiata) at 55-60 days and 130-140 days of pregnancy resulted in a significant increase in serum progesterone levels. This effect could be observed even in lutectomized monkeys. However, no significant change in the serum estrogen level was noticed. These results suggest that although no chorionic gonadotropin is detectable in the serum after 35 days of pregnancy, the foetoplacental steroidogenic system is still responsive to exogenous gonadotropic stimulation.