Expression of tPA, LH receptor and inhibin alpha, beta(A) subunits during follicular atresia in rats

By using DNA 3'-end labeling, immunocytochemistry and mRNA in situ hybridiz ation detection techniques, the expression of inhibin subunits and LH recep tor in the granulosa cells and tissue-type plasminogen activator (tPA) in t he oocytes has been studied in relation to follicular development and atres ia. The results demonstrated that: (i) tPA activity in the oocytes of norma l developing follicles is undetectable, and increases significantly in the follicle undergoing atresia; (ii) the production of inhibin subunits in gra nulosa cells is negatively correlated with the expression of oocyte tPA act ivity, indicating that they may be an important regulator of oocyte tPA pro duction and follicular development; (iii) in atretic follicles, granulosa c ells do not express LH receptor and inhibin subunits. It is therefore sugge sted that tPA may play a role in oocyte self-destruction and clearance in s ome of atretic follicles, and inhibin of granulosa-origin might be an inhib itory factor for the translation of tPA in the oocyte.