Correlation of the changes of the frequency of perichromatin granules withthe RNA content of the interchromatin region of uterine cells in normal and ovariectomized rats. A high resolution in situ hybridization and stereological study

The changes in the number of perichromatin granules (PCG) and the alteratio ns in the RNA content of the interchromatin and perichromatin regions cause d by ovariectomy and estradiol injection were studied in rat endometrial fi broblast and myometrial muscle cells. Twelve rats were divided in four grou ps. A group of rats was fixed without any treatment, the other three groups were ovariectomized and processed 21 days after the operation. One of them was studied without further treatment, and two groups were injected intrap eritoneally with 20 mu g of 17 beta-estradiol hemisuccinate and fixed 0.5 a nd 2 h after the injection. The frequency of PCG was evaluated in preparati ons stained with EDTA procedure preferential for RNP. The alterations of RN A content were estimated by post-embedding high resolution in situ hybridiz ation using a total DNA probe labeled with biotinilated nucleotides reveale d by streptavidin coupled with 10 nm gold grains. Most of the non-nucleolar labeling is associated to RNP containing fibrils. Perichromatin and interc hromatin granules are labeled to a lesser extent. Castration brings about a reduction of the number of PCG and of the numerical density of labeling in endometrial fibroblasts. The injection of estradiol causes a rapid increas e in both parameters. On the contrary, the frequency of PCG and intensity o f labeling of epithelial endometrial cells and in muscle cells increase aft er ovariectomy and are reduced by estradiol administration. These results s uggest that estradiol may affect differentially various types of target cel ls in the same organ, and also that PCG are not the only nuclear compartmen t of pre-mRNA or mRNA altered by the changes in estradiol, the RNP containi ng fibrils located in the perichromatin and in the interchromatin regions a re also involved. (C) Elsevier, Paris.