The conceptus induces a switch in protein expression and activities of superoxide dismutase 1 and 2 in the sheep endometrium during early pregnancy

•The conceptus-derived factors influence the uterine environment for conceptus implantation.•SOD is the first and most important line of defence against ROS-induced cellular oxidative damage.•The conceptus up-regulates endometrium SOD1 and SOD2 protein expression and bioactivity.

There has been a growing interest in the importance of superoxide dismutases (SODs) in the regulation of endometrial function. However, little is known about endometrial SOD1 and SOD2 protein expression and activity associated with early conceptus development. We aimed to investigate changes in protein levels and activities of SOD1 and SOD2 in the sheep caruncular (CAR) and intercaruncular (ICAR) endometrium during the transition from pre-implantation (day 14) to implantation (day 16) and post-implantation (day 18) periods of pregnancy. Lipid peroxidation was assessed by measuring CAR and ICAR malondialdehyde (MDA) content. SOD1 activity increased from day 14 to day 18 (P < 0.05) in CAR and from day 14 to day 18 (P < 0.05) and from day 16 to day 18 (P < 0.01) in ICAR. SOD1 protein level increased from day 16 to day 18 (P < 0.05) in CAR and from days 14 to days 16 and 18 (P < 0.05) in ICAR. SOD2 activity increased from day 16 to day 18 (P < 0.05) in CAR and from days 14 and 16 to day 18 (P < 0.001) in ICAR. SOD2 protein level increased from day 14 to day 18 (P < 0.05) in CAR and from days 14 and 16 to day 18 (P < 0.05) in ICAR. The content of MDA in CAR or ICAR did not alter significantly between stages of pregnancy. In conclusion, the early post-implanting conceptus co-ordinately up-regulates SOD1 and SOD2 protein expression and bioactivity within CAR and ICAR. By the maintenance of adequate endometrium SOD1 and SOD2 activity, the conceptus limits lipid peroxidation during the peri-implantation period of pregnancy.