EVOLUTION OF PROTHYMOSIN-ALPHA AND PROLIFERATING CELL NUCLEAR ANTIGEN(PCNA) IMMUNOREACTIVITY THROUGH THE DEVELOPMENT OF RAT OVARIAN FOLLICLES

The cellular distribution of prothymosin alpha (ProT) was studied in o varian follicles of adult cycling rats. We found positive granulosa an d theca cells throughout follicular maturation. When both ProT and pro liferating cell nuclear antigen (PCNA) immunoreactivity was studied, w e observed that both proteins were expressed in the same granulosa and theca cells, although sometimes ProT immunoreactivity was weak or abs ent in the mitotic (M) phase. Moreover, both peptides share the nuclea r distribution, but ProT immunoreactivity was never seen in nucleoli. Therefore, we conclude that in mitotic cells ProT is expressed only in actively proliferating cells, since all ProT-positive cells were also positive for PCNA. ProT and PCNA immunoreactivities during the meioti c division were studied in oocytes. The presence of PCNA was, unlike P roT, constant throughout follicle development (except atretic oocytes) . Oocytes expressed ProT from primordial follicles to the eighth gener ation, but more developed oocytes and atretic oocytes were not immunor eactive. In hypophysectomized rats, all oocytes were immunoreactive. I nterestingly, in hypophysectomized rats treated with follicle stimulat ing hormone (FSH) that promoted follicle development, the more develop ed oocytes did not show ProT immunoreactivity. Since hypophysectomized rats were not treated with luteinizing hormone we conclude that ProT expression is not required to complete meiotic division I.