Comparative evaluation of the dissociation rate between the vaginotrophic and uterotrphic activities of 1-hydroxy-1, 3, 5 (10)-estratriene derivatives with natural and unnatural configuration at C8 using ovariectomized mice

The agonistic and antagonistic actions of estriol

Estriol is a short acting estrogen, and as such, displays both agonistic and antagonistic properties, when it is injected in saline solution. These are predictable attributes of any short acting agonist if one considers the basic pharmacology of receptor ligand binding interactions. That is, short acting hormones or drugs occupy receptor sites for protracted time periods and, although they stimulate responses, these are of short duration. However, when estriol is administered in continuous fashion the estrogen receptor is occupied for long periods of time and full estrogenic responses are observed, and there is no antagonism of estradiol action. The purpose of this paper is to review the work that leads to the above conclusion and to discuss our more recent work on the relationship between estrogen receptor binding and the stimulation of type II estrogen binding sites.

8 alpha-Estra-1,3,5(10)-triene-1,3, 17 beta-triol as a special type of estrogen having a high vaginotrophic activity and a low uterotrophic activity in castrated mice

The vaginotrophic and uterotrophic activities of 1-OH-8-alpha-E2 and its acetate in comparison with E2 and E3 were assessed on the basis of the effect on weights, water/fat-and RNA/DNA-contents of mouse vagina and uterus. The multiple doses of 8 alpha-steroids or E3 sufficient to achieve a maximal effect on the vagina were not enough to stimulate the uterus fully. At various periods of time after multiple injections, 1-OH-8 alpha-E2 acetate was found to have a higher vaginotrophic potency than the uterotrophic potency, when compared with E2 as a standard. The study on the time course of organ response to 8 alpha-steroids, E2 and E3 after a single injection of daily dose, being equipotent when injected one daily for 3 days, demonstrated that 1-OH-8-alpha-E2 and E3 were less vaginotrophic and uterotrophic than E2 and had a short duration of action. 1-OH-8 alpha-E2 acetate in comparison with E2 produced a long-lasting vaginotrophic effect and an early regressing uterotrophic effect. It can be confirmed that 8 alpha-steroids, like E3, are a special type of estrogen having a high vaginotrophic activity and a low uterotrophic activity.