Estrogen-induced changes of ribonucleic acid in the rat uterus

The incorporation of [3H]uridine into uterine RNA of immature rats was studied up to 6 h after a single injection of estradiol. Under these experimental conditions, estradiol progressively increased the incorporation of the radioactive precursor into the total RNA. This increase could not be explained by variations in the uptake of [3H]uridine by the tissue. The total RNA and the fractions obtained by differential thermal extraction were analysed by gel electrophoresis. One hour after hormone treatment, a similar increase of incorporation of the labelled precursor in the different RNA species was observed. After a long period of time, [3H]uridine was preferentially incorporated into rRNA as compared to HnRNA and to heterogenous cytoplasmic RNA. Experiments which involved the use of low doses of actinomycin D sufficient to inhibit any rRNA synthesis, confirmed the relatively slight increase in precursor incorporation into non-ribosomal RNA. The distribution of the radioactivity incorporated into the 3 fractions of RNA, obtained by thermal extraction (2 nuclear fractions and 1 cytoplasmic), suggested an increase in the rate of transcription and transport of the RNA during hormonal treatment. The polyA-containing uterine RNA was isolated on a column of oligo(dT)-cellulose and subsequently studied by electrophoresis. There is no preferential incorporation of precursor into the polyA-containing RNA when compared with the total RNA. However, the polyA-containing RNA constitutes the only part of the non-ribosomal RNA whose synthesis continues to increase throughout the period of hormone treatment.