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The synthesis of ribonucleic acid in immature rat uterus responding to oestradiol-17 beta.

ABSTRACT: Stimulation of incorporation of labelled precursors into the RNA of immature rat uterus is an early result of oestradiol-17beta action. However, the extent of the increased incorporation varies with the mode of administration of the labelled precursors and with the weight of the rat. At the age and weight range normally used response is maximal at ten times control incorporation, 4h after the administration of 0.3mug or more of oestradiol-17beta. Under these conditions the stimulation of incorporation into the acid-soluble fraction is only 2-2.5-fold. When the purified RNA is separated on polyacrylamide gels the major increase in incorporation of radioactive precursor is found in rRNA and 4S RNA; the formation of the former has been followed from the 45S precursor. Preceding these events by at least 30min, however, is an increase in the incorporation of precursor into RNA species of very high molecular weight, which remained in the first few slices of the gel. The possible significance of these findings is discussed. The increased synthesis of rRNA in response to oestradiol-17beta is more strongly inhibited by actinomycin D than the synthesis of other RNA species. Cycloheximide, depending on time of administration and dosage, inhibits either RNA synthesis or the maturation of rRNA.

SUBMITTER: Knowler JT

PROVIDER: S-EPMC1178098 | biostudies-other | 1971 Nov

REPOSITORIES: biostudies-other

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Project description:1. The binding of [6,7-(3)H]oestradiol-17beta to uteri has been studied by using sucrose-gradient analysis and also the property of oestradiol receptors to form insoluble complexes with protamine. 2. Protamine precipitates the 8S and part of the 4S oestradiol-binding proteins in uterine cytoplasm from mature rats. It does not precipitate the oestradiol-17beta-binding proteins present in cytoplasm from non-target tissues or serum. No tritium-labelled material was precipitated by protamine after equilibration of [6,7-(3)H]oestradiol-17beta with either serum albumin or phosvitin. 3. Protamine precipitated a small amount of progesterone but not testosterone or cortisol that had been equilibrated with uterine cytoplasm. It did not precipitate any tritium radioactivity from muscle cytoplasm that had been equilibrated with either [1,2-(3)H]testosterone sulphate or [1,2-(3)H]dehydroepiandrosterone. 4. A simple method has been devised for measuring binding constants of tissue extracts for [6,7-(3)H]oestradiol-17beta, based on precipitation with protamine. Reasonable agreement was obtained between the values obtained by this method and those obtained by sucrose-gradient analysis. 5. This method has been used to study the effect of maturity, ovariectomy, adrenalectomy and hypophysectomy on the cytoplasmic binding of [6,7-(3)H]oestradiol-17beta. None of these procedures affected the dissociation constant K(d) or the number of binding sites/mg of cytoplasmic protein. When measured per uterus or per mg of DNA, ovariectomy and hypophysectomy decreased the number of binding sites. Adrenalectomy had no effect. 6. The properties of the 4S oestradiol-binding protein present in cytoplasm from mature uteri have been studied. It is not present in uteri from immature, ovariectomized, or hypophysectomized rats and it does not bind testosterone or cortisol. Unlabelled oestradiol-17beta, U-11,100A, N-ethylmaleimide and N-bromosuccinimide all decrease the binding of [6,7-(3)H]oestradiol-17beta to both 8S and 4S receptors. Binding to both 8S and 4S receptors decreases when oestradiol is transported to the nucleus. The 4S receptor is not the same as the 4S binding component formed by salt dissociation of the 8S receptor.

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The synthesis of ribonucleic acid in immature rat uterus responding to oestradiol-17 beta.

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