Mechanisms underlying antigonaclotropic effects of some traditional plant extracts in pituitary cell culture

Previous works have demonstrated that stem bark extracts of Cola nitida (Sterculiaceae), Afrormosia laxiflora and Pterocarpus erinaceus (Fabaceae) provoked a blockade of female rat ovulation and estrous cycle by inhibiting pituitary LH release in vivo. In addition, these plant extracts exerted an inhibitory effect on LH release of rat pituitary cells. Therefore, these data could explain inhibitory effects of plant extracts on LH release in vivo. The present study was undertaken to examine the mechanisms by which these plants exert their antigonadotropic activities. So, we studied the biological activities of these plant extracts on pituitary cells in culture. Data show that C. nitida, A. laxiflora and R erinaceus extracts only inhibit LH release and have no effect on FSH release. In fact, A. laxiflora, P. erinaceus and C. nitida extracts diminish LH release in culture medium without acting on rat pituitary cell content. Plant extracts form complexes with basic glycoproteins (but not with acid glycoproteins) and prevent them from entering the cells.