Regulation of [Ca2+]i Oscillations and Mitochondrial Activity by Various Calcium Transporters in Mouse Oocytes

Abstract

Oocyte activation inefficiency is one of the reasons for female infertility and Ca 2+ functions play a critical role in the regulation of oocyte activation. We used various inhibitors of Ca 2+ channels and pumps located on the plasma membrane, the endoplasmic reticulum or both, including sarcoplasmic/endoplasmic reticulum Ca 2+ ATPases (SERCAs, the main Ca 2+ pumps which decrease the intracellular Ca 2+ level by reaccumulating Ca 2+ into the sarcoplasmic reticulum), transient receptor potential (TRP) ion channel subfamily member 7 (TRPM7, a Ca 2+ /Mg 2+ -permeable non-selective cation channel), T-type Ca 2+ channels and calcium channel Orai1, to investigate their roles in[Ca 2+ ] i oscillation patterns and mitochondrial membrane potential during oocyte activation by real-time recording. Our results show that SERCAs, TRPM7 and T-type Ca 2+ channels are important for initiation and maintenance of [Ca 2+ ] i oscillations, which is required for mitochondrial membrane potential changes during oocyte activation, as well as for subsequent pronuclear formation and transition to embryo development, while the function of calcium channel Orai1 is not confirmed. Increasing the knowledge of these transporters may provide a theoretical basis for improving oocyte activation in human assisted reproduction clinics.