Suppressed expression of macrophage migration inhibitory factor in the oviducts of lean and obese cows.

Oviducts synthesise macrophage migration inhibitory factor (MIF) to promote sperm capacitation and embryogenesis. This study aimed to test a hypothesis that the oviducts of obese cows may express MIF at a lower level than those of normal and lean cows. Ampullar and isthmic oviduct sections were collected from lean (n = 5; body condition score (BCS) on a 5-point scale, 2.5), normal (n = 6; BCS, 3.0) and obese (n = 5; BCS, 4.0) Japanese Black cows. MIF mRNA and protein were extracted from ampullae and isthmuses and their levels measured by real-time polymerase chain reaction or western blot. Immunohistochemistry was performed on frozen sections of ampullae and isthmuses by using antibodies to MIF. MIF mRNA and protein expression were lower in the obese and lean groups than in the normal group (P < 0.05). Immunohistochemistry revealed that the primary site of MIF expression in the ampulla and isthmus is the tunica mucosa. In conclusion, obese cows have suppressed MIF expression in the ampullae and isthmuses of their oviducts, as hypothesised, but, unexpectedly, MIF expression was also lower in lean cows.