cAMP in ovine oocytes: Localization of synthesis and its action on protein synthesis, phosphorylation, and meiosis

✍ Scribed by Crosby, Ian M. ;Moor, Robert M. ;Heslop, John P. ;Osborn, Jeremy C.

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 938 KB
• Volume: 234
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402340217

✦ Synopsis

In the first series of experiments, the source of cAMP in the sheep oocyte was studied. Cholera toxin was shown to be a potent stimulator of cAMP in isolated sheep oocytes, demonstrating the presence of adenyl cyclase. There was no evidence for transmission of cAMP from stimulated myocardial cell monolayers to cumulus-enclosed oocytes even though the existence of a concentration gradient of cAMP and of intercellular communication were demonstrated. However, gonadotrophin-stimulated follicle shells were able to induce a rise in the cAMP content of denuded or cumulus-enclosed oocytes in the same dish, independently of cell contact. Further experiments were designed to study the effects of a cholera toxin-stimulated rise in cAMP on the maturation of oocytes. When applied to cumulus-oocyte complexes, cholera toxin did not block germinal vesicle breakdown (GVBD), nor the accompanying changes in protein synthesis and phosphorylation, although there was evidence for a delaying effect. There were, however, indications that the toxin was inducing abnormalities that became gross when the concentration was raised to 1 pg/ml. This high concentration of cholera toxin was able to block the maturation of oocytes in intact, gonadotrophin-treated follicles, although once again abnormalities were evident. We conclude that the role of cAMP in the maturation of the sheep oocyte is different from that proposed in the mouse.