Hormonal cohtrol of uterine lumen fluid retention in the rat

Abstract

Increasing amounts of lumen fluid accumulate in prepubertal rat uteri under the influence of increasing daily subcutaneous (sc) injections of estradiol-17[beta] in oil (0.05-50 [mu]g/day). Concomitant administration of progesterone, at dosages which did not cause vaginal mucification nor inhibit the uterine growth response, effectively inhibited this lumen fluid accumulation. When fluid accumulation was induced by single sc pellets of estradiol in beeswax, it disappeared within 12 hr. after a single sc injection of 1 or 2 mg progesterone administered 48-66 hr. after estradiol implantation. Ligation of cervical ends of uteri prevented this loss, indicating the cervix as the route of fluid loss and as the site of one progesterone action. When 1 mg progesterone was administered sc once daily, beginning on the day of estradiol implantation, fluid failed to accumulate even in ligated uteri, indicating a 2nd action of progesterone in inhibiting lumen fluid formation. These findings suggest the loss of uterine lumen fluid which occurs through the cervix late in estrus in the rat may be caused by the marked, but shortlived increase in progesterone secretion which occurs at proestrus.