Correlation between frequency of nuclear bodies and expression of estradiol receptors in endometrial epithelial cells of old rats

Abstracts of the ISGSH Meeting CORRELATION BETWEEN FREQUENCY OF NUCLEAR BODIES AND EXPRESSION OF ESTRADIOL RECEPTORS IN ENDOMETRIAL EPITHELIAL CELLS OF OLD RATS L. Staneva-Dobrovski. Department of Neuroanatomy, H. Heine University of Diisseldorf, Germany Nuclear bodies (NB) are dynamic substructures in the interchromatin of interphase nuclei, regarded as markers of stimulated rRNA synthesis. We have shown earlier that during the rat estrous cycle, the frequency of complex nuclear bodies in endometrial cavum and glandular epithelial cells is temporally correlated with the expression of estrogen (ER) and progesterone (PR) receptors and is estrogen dependent. The present study was designed to simultaneously examine the frequency of simple and complex NB and the status of ER in endometrial epithelium of old rats in relation to age and vaginal cytology. Wistar rats with daily monitored vaginal smears for at least 180 days were used at 24, 28, 32, and 36 months of age (three rats per age group). NB were counted in one ultrathin section for each of three tissue blocks per animal. Thirty-two, 33, or 34 adjacent cells were selected for analysis in each of these sections. Thus, the frequency of NB per animal was calculated as the number of NB observed in 100 epithelial cells. In the light microscope, the percentage of immunopositive nuclei (out of 300 cells per animal) was evaluated tbr ER using MAB and Bio Strept immunodetect system (BioGenex, generous gift from DCS Innov. DiagnostikSystem, Hamburg) on paraffin sections after microwave antigen retrieval. Old rats exhibited extremely irregular cycles with a predominance of persistent estrus or anestrus phases over many days or even weeks. In all age groups, the percentage of ER-immunopositive nuclei was maximal in the endometria of rats in estrus, which had persisted over 2-3 months. NB were particularly numerous (2-3 complex NB out of 4-5 MN per nucleus) in unusually tall epithelial cells that showed ultrastructural signs of intense protein synthesis and secretion in uteri of these rats. The isolated simple NB in nuclear profiles of inactive, low epithelial cells in rats in persistent anestrus correlated with an almost absent ER expression. Endometrial ER synthesis is probably down-regulated only in rats in persistent anestrus whereas in persistent estrus ER, expression coincides with high NB frequency in the epithelial cells. Our findings show, tbr the first time, that ER expression and NB frequency in endometrial epithelial cells are estrogen-dependent also in old rats and suggest that unopposed long-acting endogenous estrogens can induce proliferation and differentiation in the endometrium of even old rats.

PROLIFERATING CELL NUCLEAR ANTIGEN, ESTRADIOL AND PROGESTERONE RECEPTORS AS MARKERS FOR DIFFERENT PHASES OF RAT ESTROUS CYCLE L. Staneva-Dobrovski,* Ch. Hauke,t and H. Korrt *Department of Neuroanatomy, H. Heine University of Dtisseldorf; and tDepartment of Anatomy, RWTH Aachen, Germany Proliferating cell nuclear antigen (PCNA), an auxiliary protein of DNA polymerase-delta, is closely linked to cell replication and present during G1, S, and G2/M phases of the cell cycle. In the cascade of cyclic modulations in the endometrium, cell proliferation is followed by growth and differentiation, manifested among others by the synthesis of cell-specific proteins. To study the interrelations between proliferative activity and synthesis of specific receptor proteins in the main cell populations of the cyclic endometrium, we immunohistochemically examined the expression of PCNA, estrogen, and progesterone receptors (ER and PR). The expression of the markers under study was evaluated as the percentage of immunopositive nuclei out of 200 cells per cell type/animal (cavum and glandular endometrial epithelium, stroma fibroblasts). Wistar rats (n = 20; 3 months of age), with daily monitored vaginal cytology tbr at least three consecutive 4-day estrous cycles, were used at each of the four phases. PAP-immunohistochemistry with monoclonal PC I0 PCNA-antibody (Dakopatts, Denmark) was applied on paraffin sections from tbrmalinfixed uterine horns. ER and PR were identified using MABs and Bio-Strept immunodetection system (Biogenex, generous gift from DCS Innov. Diagnostic Systeme, Hambug) on uterine paraffin sections after microwave antigen retrieval. PCNA expression in nuclei of cavum and glandular epithelial cells was maximal at diestrus, whereas most fibroblasts in the central endometrial stroma were immunopositive at proestrus, in full concord with earlier autoradiographic findings. Percentages of ER- and PR-positive nuclei in cavum and glandular epithelia were highest at estrus and declined during metestrus, whereas central stroma fibroblasts expressed both ER and PR intensely at estrus and early metestrus. Our findings demonstrate that PCNA, ER, and PR are markers for different phases of the estrous cycle in the rat endometrium: PCNA is high during diestrus (cavum/gland epithelia) and proestrus (central stroma fibroblasts); whereas ER and PR expression in the main cell populations coincide with high estrogen levels at estrus. Thus, proliferative activity and the synthesis of specific receptors for estrogen and progesterone are inversely related in the cyclic rat endometrium.

Steroids, 1997, vol. 62, November

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