We previously reported that the serine protease plasmin plays a role in follicle rupture during ovulation in the teleost medaka. In this study, we showed that urokinase-type plasminogen activator 1 (Plau1) is a physiological activator of plasminogen. Morphological analyses revealed that in the preovulatory follicle, plau1 mRNA was detected in association with follicle cells, while Plau1 protein was localized in the oocyte egg membrane. Both an inactive precursor and an active form of Plau1 were present at constant levels in the membrane fraction via the latter half of the 24-h spawning cycle. Plasminogen activator inhibitor-1 (Pai1) was detected in the follicle layer of the preovulatory follicle, but the protein level was low at approximately 7 h prior to ovulation. We showed that plasmin hydrolyzed laminin, which is a major component of the basement membrane and is situated between the granulosa and theca cells of the follicle. In vitro ovulation of large follicles was significantly inhibited by anti-Plau1 antibodies and active recombinant Pai1. Levels of Pai1 expression were increased in vivo at approximately 7 h prior to ovulation. Expression of Pai1 was also induced in vitro in the follicle with recombinant medaka luteinizing hormone (Lh). Lh-induced expression of pail mRNA was significantly suppressed by the presence of MDL (an adenylyl cyclase inhibitor), trilostane (a 3beta-hydroxysteroid dehydrogenase inhibitor), and RU486 (a nuclear progestin receptor antagonist). These results support our recent proposal of a sequential two-step ECM protein hydrolysis model for follicle rupture for medaka ovulation.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 92 • No. 1