PRECOCIOUS OOCYTE MATURATION IS INDUCED BY AN INHIBITOR OF CAMP-DEPENDENT PROTEIN-KINASE IN THE INTACT GOLDEN-HAMSTER

The purpose of this investigation was to determine if precocious oocyt e maturation could be induced by modulating ovarian cAMP-dependent pro tein kinase (PKA) or protein kinase C (PKC) signal transduction pathwa ys in the intact hamster. The following inhibitors and stimulators wer e injected into the ovarian bursal cavity of the anesthetized hamster: romocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), a relative ly selective inhibitor of PKA phosphorylations; a structurally related compound, H-7, a less potent and selective inhibitor used to alter PK A and PKC pathways; phorbol 12, 13-didecanoate (PDD beta), an active s timulator of PKC and the inactive analog, 4 alpha-phorbol 12,13-dideca noate (PDD alpha); and GF109203x, a potent and selective inhibitor of PKC phosphorylations. The experimental design was to inject the modula tor into the bursal cavity of one ovary and control solution of diluen t or inactive compound into the contralateral bursal cavity. After 1 h r oocytes were collected and evaluated microscopically for the presenc e or absence of a germinal vesicle. Only oocytes recovered from H-89 t reated ovaries (>50 mu M) showed significantly greater frequency of me iotic resumption. Exposure of ovaries to H-7 (less than or equal to 15 0 mu M), PDD beta (less than or equal to 100 mu M), or GF109203x (less than or equal to 100 mu M) did not significantly affect oocyte matura tion state. These results suggest that ovarian protein phosphorylation s carried out by PKA are necessary for the maintenance of oocyte meiot ic arrest in situ. (C) 1995 Wiley-Liss, Inc.