Maintenance of meiotic arrest by increasing [cAMP]i may have physiological relevance in bovine oocytes.
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.
Aktas
H
H
Department of Meat and Animal Science, University of Wisconsin, Madison 53706, USA.
Wheeler
M B
MB
First
N L
NL
Leibfried-Rutledge
M L
ML
D000262:Adenylyl Cyclases / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001886:Bordetella pertussis / Q000201:enzymology; D002417:Cattle / Q000502:physiology*; D002478:Cells, Cultured; D003470:Culture Media; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D007424:Intracellular Fluid / Q000201:enzymology*; D007546:Isoquinolines / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology; D011418:Prophase / Q000187:drug effects*; D013449:Sulfonamides; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors
D003470:Culture Media; D007546:Isoquinolines; D013449:Sulfonamides; D013873:Thionucleotides; C016957:adenosine-3',5'-cyclic phosphorothioate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide