LOCALIZATION AND PARTIAL CHARACTERIZATION OF A RAT OVARIAN GRANULOSA-CELL PROTEIN WITH A MONOCLONAL-ANTIBODY

Hybridoma cell lines were obtained from mouse splenocytes sensitized t o granulosa cells collected from rat ovaries after gonadotropin stimul ation. A monoclonal antibody (5G5) was obtained which reacted with gra nulosa cells and showed a positive reaction with serum-free conditione d medium containing granulosa cell secreted proteins. Immunoblotting o f the conditioned medium and light- and electron-microscopic immunocyt ochemistry of rat ovary show that mAb 5G5 is directed against a 59-kDa protein which is located on the plasma membrane of granulosa cells. F urthermore, the immunoreactivity of the granulosa cells depends both o n the degree of follicle development and on the position of the granul osa cells within the follicles. Strong immunoreactivity was observed i n the innermost granulosa cell layers, close to the oocyte and the ant ral cavity. The results obtained show that mAb 5G5 is a useful marker of a 59-kDa granulosa cell protein which might be of importance for th e development of the follicle and the oocyte maturation.