Endocrinology, Vol 133, 2127-2132, Copyright © 1993 by Endocrine Society

ARTICLES

Possible involvement of protein kinase C in gonadotropin-induced ovulation in the rat ovary

T Shimamoto, M Yamoto and R Nakano
Department of Obstetrics and Gynecology, Wakayama Medical College, Japan.

Recent reports indicate that protein kinase C may play an important role in the process of gonadotropin-induced ovulation in the ovary. In the present study, we examined the effect of the protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), on LH- stimulated tissue type plasminogen activator (tPA) activity in cultured rat granulosa cells. Granulosa cells were obtained from PMSG-treated rats and cultured for 48 h in the presence or absence of H-7 (0.1-60 microM) with ovine LH (30 ng/ml), phorbol 12-myristate 13-acetate (10(- 8) M), phorbol 12,13-dibutyrate (10(-8) M), or (Bu)2cAMP (5 mM). After culture, tPA activity in the conditioned medium was assayed by fibrin autography technique after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. H-7 (1.0-60 microM) inhibited LH-, phorbol 12- myristate 13-acetate-, or phorbol 12,13-dibutyrate-stimulated tPA activity dose dependently, and each ID50 was approximately 8 microM. However, H-7 did not inhibit (Bu)2cAMP-stimulated tPA activity. To investigate the effect of H-7 on the ovulatory process in vivo, PMSG- treated immature rats were injected with H-7 (10(-9)-10(-3) M) into the unilateral ovarian bursa just before human CG administration. After 24 h, the number of oocyte-cumulus complexes in the oviduct was counted. H- 7 suppressed the number of oocytes released from treated ovaries dose- dependently. The light microscopical observation revealed that ovaries treated with H-7 contained a few corpora lutea and many large unruptured follicles. The results of the present study suggest that the suppressive effects of H-7 on human CG-induced ovulation might be partly due to the inhibition of tPA secretion by rat granulosa cells via protein kinase C inhibition.

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