Maintenance of meiotic arrest by increasing [cAMP](i) may have physiological relevance in bovine oocytes

H. Aktas, M. B. Wheeler, N. L. First, M. L. Leibfried-Rutledge

Research output: Contribution to journalArticlepeer-review

Abstract

Invasive adenylate cyclase (iAC) reversibly inhibits spontaneous maturation of cumulus-enclosed bovine oocytes by increasing the intracellular concentration of cAMP, [cAMP](i). In this study, physiological aspects of maintaining meiotic arrest in bovine oocytes by iAC were investigated. The maintenance of germinal vesicle arrest by iAC in both cumulus-enclosed and denuded bovine oocytes was concentration dependent (r2 = 0.857). Denuded bovine oocytes were more sensitive to maintenance of meiotic arrest by iAC then were cumulus-enclosed oocytes. At the highest concentration, 70% of the cumulus-enclosed and 90% of the denuded bovine oocytes were maintained in meiotic arrest. The iAC increased [cAMP](i) in both intact cumulus-oocyte complexes and enclosed oocytes in a concentration-dependent manner (r2 = 0.795). Cumulus-enclosed oocytes maintained in meiotic arrest by iAC retained developmental competence when subsequently cultured in iAC-free medium and then fertilized. The [cAMP](i) in bovine complexes decreased precipitously upon release from follicles and remained low for the next 125 min. However, the [cAMP](i) of the enclosed oocytes did not change. Bovine oocytes commit to undergo meiosis in a progressive manner. Approximately 10% of the oocytes were already committed when aspirated. This proportion increased to 40% at 2 h and 70% at 5 h. Use of two inhibitors of cAMP-dependent protein kinase A provided further evidence that cAMP functions in mediating meiotic arrest in bovine oocytes. Bovine oocytes, therefore, are sensitive to different cAMP concentrations, and are developmentally competent after iAC-induced arrest, and complexes containing oocytes exhibit a decrease in [cAMP](i) before spontaneous maturation. These results suggest that maintenance of meiotic arrest by iAC is accomplished through modulation of cellular machinery, and regulation of oocyte maturation by [cAMP](i) may be physiologically relevant.

Original languageEnglish (US)
Pages (from-to)237-245
Number of pages9
JournalJournal of Reproduction and Fertility
Volume105
Issue number2
DOIs
StatePublished - Jan 1 1995
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Embryology
  • Molecular Biology
  • Obstetrics and Gynecology
  • Developmental Biology

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