Autoradiographic studies on [³H]oestradiol localization in the blastocysts and uterus of rats during delayed implantation

Abstract

The present studies were undertaken to obtain information about the localization of oestradiol in rat blastocysts and to elucidate the interrelationship between hormone localization and function. Tritiumlabelled oestradiol was administered intraluminally into the uterus or subcutaneously in rats in which implantation was delayed by ovariectomy on Day 3 post coitum followed by treatment with progesterone. Rats were killed 5, 15 and 30 min after intraluminal instillation or 5, 15 and 60 min after subcutaneous injection of [³H]oestradiol. Autoradiograms of flushed-out blastocysts as well as a blastocyst in situ showed no retention and subcellular concentration of radioactivity while, in uterine stromal, glandular and muscle cells, characteristic nuclear concentration and retention of the steroid were observed. Since blastocysts are metabolically activated by treatment with oestradiol, several possible mechanisms are discussed to explain the activation of blastocysts in the apparent absence of oestradiol-binding proteins in cells of the blastocysts