Osmolarity at early culture stage affects development and expression of apoptosis related genes (bax-α and bcl-xl) in pre-implantation porcine NT embryos

This study examined whether high osmolarity of culture medium at the early culture stage affects development and expression of apoptosis related genes (Bax‐α and Bcl‐xl) of porcine nuclear transfer (NT) and in vitro fertilization (IVF) embryos. NT and IVF embryos were divided into three groups and the basic medium was PZM‐3 (260–270 mOsmol, control group). The control group of embryos was cultured in PZM‐3 for whole culture period. Other two groups of embryos were cultured in a modified PZM‐3 with 0.05 M sucrose (300–320 mOsmol, sucrose group) or increased NaCl to 138 mM (300–320 mOsmol, NaCl group) for the first 2 days, and then cultured in PZM‐3 for 4 days. NT embryos cultured in NaCl group showed a significantly higher developmental rate to the blastocyst stage with a decreased apoptosis rate compared to the control (P