Detection of Early Pregnancy Factor in the Sera of Cows Whose Uteri were Infused with Trophoblastic Cell Culture Medium.

Abstract

The aim of this study was to examine whether or not uterine infusion with a medium showing positive early pregnancy factor (EPF) activity influences maternal physiology in cattle. Trophoblastic cells derived from 12-day-old bovine embryos were cultured in Dulbecco's PBS (+) at 39 C in air for 24 h. EPF activity was assayed using the rosette inhibition test. A rosette inhibition titer (RIT) above 4 was regarded as indicating positive EPF activity. The trophoblastic cell culture medium (Tro-CM) showed positive EPF activity. On days 7 to 12 after estrus, five cows each received a nonsurgical infusion of Tro-CM (0.25 ml) in the lumen of the uterine horn. Blood samples were collected daily by the tail artery or vein puncture from day 0 (the day of infusion) to day 5. All five cows showed positive EPF activity in their sera on days 2 to 4, and three cows out of the five kept showing positive EPF activity for 2 to 3 days. The result demonstrated that sera of cows infused with a small amount of EPF-positive medium (Tro-CM) into the uterus showed temporary positive EPF activity in maternal serum, further suggesting that EPF released from Tro-CM would induce a release of maternal EPF, but not by directly entering into the maternal blood flow.