| Abstract: | Comparative study, through radiochemical analysis, of the binding of estrogens to the uterine and pituitary receptors in immature rats showed that, for binding to the uterine recpetors, a free OH group in Position 3 is necessary. 17alpha-ethinyl estradiol as well as mestranol (17alpha-ethinyl estradiol-3-methyl ether), showed a stronger affinity for the pituitary than the uterine receptors. Indeed, mestranol, among the 3-methyl ether estrogens, has a special place in respect to its affinity for the pituitary. Since the binding to the receptors is an essential stage in inhibition or stimulation effects, this is a significant point. It may be that mestranol exercises its recognized central effect not only indirectly through release of ethinyl estradiol, but also directly. |
