POLY (ADENOSINE DIPHOSPHATE-RIBOSE) SYNTHESIS IN THE ANTERIOR-PITUITARY OF THE FEMALE RAT THROUGHOUT THE ESTROUS-CYCLE - STUDY OF POSSIBLE RELATION TO CELL-PROLIFERATION AND PROLACTIN GENE-EXPRESSION

To investigate whether cell proliferation and PRL gene expression in f emale rat pituitary during estrous cycle were mediated by the poly (AD P)-ribosylation of chromatin proteins, anterior pituitaries at differe nt estrous cycle were obtained from female Wistar rats, and poly (ADP- ribose) synthesis, DNA synthesis, PRL and GH messenger RNAs and PRL co ntent in the pituitary, and serum concentrations of PRL and estradiol were analyzed. From diestrus to proestrus, poly (ADP-ribose) synthesis , the contents of PRL messenger RNA and PRL in the pituitary increased significantly, and decreased at estrus. However, DNA synthesis and se rum concentration of PRL showed a significant increase from proestrus to estrus. Serum estradiol concentration increased from diestrus to pr oestrus. No significant change was observed in the pituitary GH messen ger RNA content during estrous cycle. The increase of PRL messenger RN A from diestrus to proestrus was abolished completely by the administr ation of nicotinamide, an inhibitor of poly (ADP-ribose) synthesis, to rats at diestrus. These results indicate that poly (ADP)-ribosylation of chromatin proteins may play some role in cell proliferation and tr anscription of PRL gene during rat estrous cycle.