Exogenous dibutyryl cAMP affects meiotic maturation via protein kinase A activation; it stimulates further embryonic development including blastocyst quality in pigs

Abstract

High concentrations of cyclic AMP in germinal vesicle oocytes generally inhibit GVBD. Thus, maintaining the GV stage in growing oocytes is essential for the developmental competence of the eggs. In this study, we traced the effects of dibutyryl cyclic AMP on meiotic maturation and early embryonic development in pigs. We also investigated several blastocyst qualities, including structural integrity, mitochondrial membrane potential, and apoptosis, which are affected by dbcAMP. To determine whether increased concentrations of cAMP inhibit GVBD, we explored the meiotic patterns and during maturation of pig oocytes. When treated with dbcAMP for 22 h, 91.1% of the oocytes were arrested in the GV stage compared to only 38.8% of the oocytes in the control group (P < 0.05). After completion of IVM, a higher proportion of the dbcAMP-treated oocytes were in metaphase 11 than the untreated ones (91.3% vs. 72.8%, P < 0.05). Western blot analysis showed a reduction (at 22 h) and/or increase (at 44 h) in MPF and MAP kinase activities in porcine oocytes treated with dbcAMP for the first 22 h of IVM compared to the untreated control. We also confirmed that protein kinase A activity increased in dbcAMP-treated oocytes, indicating an elevated intracellular concentration of cAMP. After IVF, the frequency of polyspermy in the dbcAMP-treated group decreased compared to that in the control group (22.4% vs. 47.4%, P < 0.05). Furthermore, blastocyst formation, the blastocyst cell number, mitochondrial membrane potential, and apoptosis were enhanced and/or reduced by dbcAMP in both IVF and SCNT embryos. We concluded that synchronizing meiotic resumption by dbcAMP treatment improved the developmental capacity and embryonic qualities of IVF and SCNT embryos by increasing the mitochondrial membrane potential and decreasing the incidence of apoptosis in preimplantation-stage porcine embryos. (C) 2008 Elsevier Inc. All rights reserved.