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To test the hypothesis that inhibition of protein kinase (PK) activity or proteolysis inhibits ovulation.Rats were injected intrabursally with protein kinase (H9 or staurosporin) or proteinase (alpha 2-macroglobulin) inhibitors and oocyte release was evaluated.Clinical Research Laboratory, Center for Reproductive Medicine, University of Kentucky Medical Center.Immature rats stimulated with pregnant mare serum gonadotropin.Staurosporin (1 or 10 microM), H9 (1 mM), alpha 2-macroglobulin (835 microIU of activity); or vehicle was injected into the right ovarian bursa. The left ovarian bursa remained intact. Animals immediately received human chorionic gonadotropin (hCG).Analysis of oocyte release and ovarian morphology.Oocyte release from the inhibitor-treated side decreased for the H9 group (8.1 +/- 1.9 fewer oocytes released, P less than 0.001) and the 10 microM staurosporin group (5.5 +/- 0.6, P less than 0.001). No change in oocyte release was observed in the 1 microM staurosporin, alpha 2-macroglobulin, or vehicle injected groups. Histologic examination of vehicle treated ovaries demonstrated numerous developing corpora lutea (CL; 20.5 +/- 2.1 CL/ovary) and a lack of preovulatory follicles. In contrast, ovaries treated with PK inhibitors contained unruptured preovulatory follicles coincident with fewer forming CL (11.5 +/- 3.5 CL/ovary).Inhibition of PK activity in vivo suppresses ovulation, demonstrating that protein phosphorylation plays an important intermediary role in the ovulatory process. |
