Serum and Placental Oxytocinase in Healthy Late Pregnant and Postpartum Mares

Oxytocinase (OTase)/insulin regulated aminopeptidase (IRAP) or leucyl-cystinyl aminopeptidase (LNPEP) varies in pregnant women with higher levels in the third than the first trimester of pregnancy. Oxytocinase is present in the chorionic microvilli of human placenta, hydrolyzes several peptides including oxytocin and vasopressin, and is suggested to be responsible for maintaining pregnancy homeostasis. There is paucity of information on the activity and presence of OTase in placental tissues and serum of pregnant mares. The objectives of this study were: 1) characterize serum OTase of pregnant mares in the last month of gestation and post-partum; and 2) characterize the effect of location on OTase expression in placental tissues of mares. Jugular blood samples were taken from 18 Standardbred mares: (a) prepartum (320-336 days of gestation), (b) 24 hours before parturition, (c) 20 minutes and (d) 2 hours after foaling. Serum was stored frozen until analysis ...