Expression of plasminogen activator (PA) and a PA inhibitor in human granulosa cells from preovulatory follicles.

Abstract

Studies with rat ovarian cells indicate that proteolytic enzymes, such as plasminogen activator (PA), play a role in the tissue remodeling that occurs before ovulation. In the rat, gonadotropins appear to increase granulosa cell tissue-type plasminogen activator (t-PA) content by increasing the cellular concentration of t-PA mRNA as well as by modulating the activity of a specific PA inhibitor (PAI). We obtained granulosa cells from preovulatory follicles of women undergoing either in vitro fertilization or gamete intra-fallopian tube transfer in order to evaluate the roles of PA and PAI in human ovulation. Samples of granulosa cell total RNA were hybridized with probes for t-PA, urokinase-type PA, PAI type 1 (PAI-1), or inhibin A-chain (as a control). Northern analyses revealed that the RNA of granulosa cells from preovulatory follicles contained little or no detectable PA mRNA. In contrast, two species of PAI mRNA were detected in relative abundance. The signal intensity produced by the PAI-1 probe varied by about 8-fold among patient samples, suggesting that PAI-1 may be useful as a marker of follicular maturation and differentiation. These results demonstrate that human granulosa cells collected immediately before ovulation contain PA inhibitor mRNA, yet have little or no PA mRNA.