Molecular Pharmacology, Vol 9, 520-533, Copyright © 1973 by the American Society for Pharmacology and Experimental Therapeutics

Comparative Study of Estrogen Action

¹ Centre de Recherches Roussel-Uclaf, 93230 Romainville, France

By comparing 16 estradiol derivatives, it has been possible to assess the relative influence of distribution, metabolism, uterine uptake, and plasma and tissue binding on uterotrophic activity in the rat. This comparison has revealed that all active compounds are bound in vivo to the 8 S uterus cytosol receptor, but that their activity cannot be related to binding in vitro, owing to the many factors acting on the compound in vivo prior to the triggering of the biological response. It is suggested that only the free molecule in the plasma is active on the uterus and that consequently activity is modulated by plasma binding.