Expression of tPA, LH receptor and inhibin a,βA subunits during follicular atresia in rats

By using DNA 3′-end labeling, immunocytochemistry and mRNA insitu hybridization detection techniques, the expression of inhibin subunits and LH receptor in the granulosa cells and tissue-type plasminogen activator (tPA) in the oocytes has been studied in relation to follicular development and atresia. The results demonstrated that: (i) tPA activity in the oocytes of normal developing follicles is undetectable, and increases significantly in the follicle undergoing atresia; (ii) the production of inhibin subunits in granulosa cells is negatively correlated with the expression of oocyte tPA activity, indicating that they may be an important regulator of oocyte tPA production and follicular development; (iii) in atretic follicles, granulosa cells do not express LH receptor and inhibin subunits. It is therefore suggested that tPA may play a role in oocyte self-destruction and clearance in some of atretic follicles, and inhibin of granulosa-origin might be an inhibitory factor for the translation of tPA in the oocyte. Project supported by the National Natural Science Foundation of China (Grant Nos. 39770099 and 39770290), Chinese Academy of Sciences and Rockefeller Foundation/WHO HPR research project.