S-nitroso-N-acetyl penicillamine inhibits spontaneous exit from metaphase-II arrest in rat eggs cultured in vitro.

BACKGROUND: Present study was designed to investigate the in vitro effects of nitric oxide (NO) donor such as S-nitroso-N-acetyl penicillamine (SNAP) on spontaneous exit from metaphase-II arrest (SEM-II) in rat eggs cultured in vitro.

METHODS: Ovulated eggs were denuded and then exposed to various concentrations (0.0, 0.01, 0.1 and 1.0mM) of SNAP for 3h under in vitro culture conditions. The percentage of SEM-II, specific and total phosphorylated cyclin-dependent kinase-1 (Cdk1), cyclin B1 and anaphase promoting complex/cyclosome (APC/C) levels as well as Cdk1 activity were analyzed.

RESULTS: The SEM-II was associated with a decrease of Thr-161 phosphorylated Cdk1 as well as cyclin B1 levels and increase of Thr-14/Tyr-15 phosphorylated Cdk1, APC/C levels and Cdk1 activity in aged eggs cultured in vitro. On the other hand, SNAP treatment prevented a decrease of Thr-161 phosphorylated Cdk1 as well as cyclin B1 levels and increase of Thr-14/Tyr-15 phosphorylated Cdk1, Cdk1 activity that finally prevented SEM-II in a concentration-dependent manner. However, APC/C level was not affected by SNAP during the course of treatment in vitro.

CONCLUSIONS: Present data suggest that SNAP prevented SEM-II possibly by increasing high level of NO and thereby maturation promoting factor (MPF) stabilization in rat eggs cultured in vitro. Hence, SNAP could be used to prevent SEM-II that reduces reproductive outcome in several mammalian species.