Intracellular levels of hydrogen peroxide and nitric oxide in oocytes at various stages of meiotic cell cycle and apoptosis

Abstract

The objective was to find out the functional roles of hydrogen peroxide (H₂O₂) and nitric oxide (NO) during various stages of meiotic cell cycle and apoptosis in rat oocytes. For this purpose, 30 oocytes from each stage such as diplotene, metaphase-I (M-I), metaphase-II (M-II) and apoptosis were collected and intracellular H₂O₂, total nitrite level and inducible nitric oxide synthase (iNOS) expression were analysed. This study demonstrated that generation of a tonic level of H₂O₂ induces meiotic resumption in diplotene-arrested oocytes and further increase may lead to apoptosis. Conversely, reduction in iNOS expression and total nitrite level are associated with meiotic resumption in diplotene-arrested oocytes, but induce apoptosis in aged oocytes. These results suggest that generation of a tonic level of H₂O₂, reduced iNOS expression and total nitrite level are associated with meiotic resumption, while more generation of H₂O₂ and sustained reduced total nitrite level are linked with oocyte apoptosis in rat.

• Hydrogen peroxide
• total nitrite level
• oocyte
• meiotic cell cycle
• apoptosis
• rat