Microinjection of inositol 1,4,5–trisphosphate into sheep and hamster oocytes induces secretion of cortical granules in a dose-dependent manner. In the sheep, this effect is strongly pH-dependent with minimal exocytosis taking place at pH 6·8 but a full cortical reaction occurring at pH 8·0. Exocytosis in the hamster is also affected by the pH of the external medium but to a lesser extent. Injection of GTPγS also induces exocytosis in both species but is more effective in the hamster. It is suggested that inositol metabolism stimulated by sperm-egg interaction with a GTP-binding protein may be part of the mechanism leading to cortical granule exocytosis and that this may be modulated by the external pH.

Keywords:
sheep, hamster, oocyte, cortical reaction, inositol trisphosphate, pH
© 1988 by Company of Biologists
1988
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