Administration of oestradiol-17β to ovariectomized rats increases the incorporation of [32P]orthophosphate into RNA, phosphoproteins and phospholipids of the uterus. Uteri taken from the ovariectomized rats pretreated with oestradiol for 1 h in vivo continued to manifest enhanced ability to incorporate 32P into RNA, phospholipids and phosphoproteins when tested in vitro. However, when oestradiol was added directly to the incubation medium, it failed to stimulate to the same extent the incorporation of [32P]orthophosphate into RNA and phosphoproteins in excised uteri from ovariectomized rats. An increase in the incorporation of 32P into phospholipids was obtained only after prolonged incubation of the excised uteri in the medium containing oestradiol.
A number of experimental approaches has been tried to reproduce more completely the in-vivo actions of oestradiol on the rat uterus in vitro. Supplementation of the medium with hormones such as insulin, progesterone and biogenic amines like adrenaline, histamine and serotonin besides oestradiol was not sufficient to attain the metabolic capacities of the uterus from animals primed with oestradiol in vivo. Oestrone was not effective. The presence of tissues such as liver, parametrial fat, adrenal glands or anterior pituitary in the incubation medium did not modify the lack of full response of ovariectomized rat uteri to oestradiol in vitro.
Studies were also extended to uteri incubated in the peritoneal cavity of ovariectomized rats instead of in synthetic media. Moreover the uteri of rats in pro-oestrus and dioestrus were also tested in vitro for their lack of full invivo-like response to oestradiol.
Cyclic 3′,5′-AMP and AMP stimulated in vitro the incorporation of [32P]orthophosphate into RNA but not into phosphoproteins and phospholipids.
Results are discussed and arguments made for the lesion possibly preventing the full development of the uterotropic action of the hormone in vitro, even though limited effects of the hormone were obtained.
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