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

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.

A comparison of the effects of oestrogen and tamoxifen on the synthesis of uterine high molecular mass RNA

“…Clearly, the synthesis of uterine rRNA is strongly stimulated at 2 h after oestrogen administration and the response appears to result from increased transcription of the 45 S rRNA precursor. These results confirm [2]. It is notable that the peaks of radioactive precursor incorporation into rRNA and rats, (30-35 g) received a subcutaneous injection of 0.1 ml comoil2 h before death.…”

“…It can be seen that, 2 h after the administration of 11.18 oestradiol-17/3/30-3 5 g rat, there was a marked stimulation in the incorporation of precursor into 28 S and 18 S RNA. This increased synthesis could be followed through the 45 S and 32 S pre-rRNA species by varying the time of precursor incorporation and by cofractionating with 14C-labelled 45 S and 32 S RNA isolated from HeLa cell nucleoli [2]. The 32 S species is detectable in the 2 h oestrogen treatment panel of fig.2 as a peak of radioactivity migrating slightly slower than the 28 S species.…”

The Incorporation of Newly Synthesized RNA into Nuclear Ribonucleoprotein Particles after Oestrogen Administration to Immature Rats

“…The reagents, experimental animals, injection techniques, incubation in vitro, preparation of acidsoluble and acid-insoluble fractions, preparation of total uterine RNA and electrophoresis of RNA on polyacrylamide gels have been previously described [1,21.…”

“…The protein was fractionated on 8.77; polyacrylamide gels which were run until the marker dye (bromophenol blue) was 1 cm from the far end. The gels from left to right are (A) uterine chromatin nonhistone protein, (8) protein from uterine ribonucleoprotein particles, (C) 40-S subunit ribosomal protein, (D) 60-S subunit ribosomal protein and (E) 80-S ribosomal protein times after the administration of oestrogen to immature rats [1,2]. The present study forms part of a continuing investigation of the role of this hnRNA in oestrogen action and attempts to demonstrate Excised uteri of each group were incubated in 2 ml of Eagles medium containing 10 pCi/ml [5-3H]uridine as in Methods.…”

“…This is followed by an increase in the synthesis of rRNA and tRNA which is detectable 1 -2 h after oestrogen administration and reaches a peak of up to 12 times unstimulated levels 2-4 h after hormone treatment [l]. Studies with inhibitors [1,3] indicate that the production of rRNA is dependent on the preliminary synthesis of hnRNA and on protein synthesis. Since an increasing body of evidence supports the view that at least a part of hnRNA is a precursor of mRNA [4,5], it has been proposed that the primary action of oestrogen might be to stimulate the synthesis of specific messengeri in the form of hnRNA.…”