SECRETION OF BOVINE UTERINE PROTEINS IN RESPONSE TO TYPE-I INTERFERONS

Bovine interferon-tau (bIFN-tau) is secreted by the developing concept us and initiates antiluteolytic events by interacting with uterine mem brane receptors. We have identified three endometrial proteins (simila r to 8, 16, and 28 kDa; P8, P16, and P28; respectively) that are secre ted in response to recombinant (r) bIFN-tau. The objective of this stu dy was to determine whether or not secretion of these proteins was a u nique response to IFN-tau during early pregnancy. Three experiments we re designed to examine secretion of endometrial proteins as a function of time in culture (0, 3, 6, 12, 18, 24 h), stage of the estrous cycl e and pregnancy (Days 15, 18, 0/21), and dose of Type I IFN (0, 0.5, 5 , and 25 nM; rbIFN-tau, rbIFN-alpha, and roIFN-tau). Endometrium was c ultured for times specified with L-[H-3]leusine to generate radiolabel ed proteins. Secreted proteins were quantitated by using one-dimension al (1D)-PAGE, fluorography, and densitometry. Secretion of P8, P16, an d P28 increased over time (p < 0.0001) in culture and in response to 2 5 nM rbIFN-tau (p < 0.05). Secretion of P8 in response to rbIFN-tau wa s higher (p < 0.0005) in endometrium collected from pregnant than nonp regnant heifers, but did not differ across the days examined. Although secretion of P8 was higher (p < 0.0001) in the presence than in the a bsence of rbIFN-tau, it was not affected by rbIFN-alpha. Secretion of P16 was higher (p < 0.0001) in endometrium collected from pregnant tha n from nonpregnant heifers, but did not differ across the days examine d. Both rbIFN-tau and rbIFN-alpha stimulated (p < 0.0005) secretion of P16, but this effect was significant only in tissues collected during the estrous cycle. Pregnancy status, day of collection, and treatment with rbIFN-alpha did not affect secretion of P28. However, rbIFN-tau stimulated (p < 0.001) secretion of P28. Dose-response studies reveale d that secretion of P8 and P28 was stimulated in a dose-dependent mann er only by rbIFN-tau (p < 0.005). Secretion of P16 was stimulated by a ll Type I IFNs examined (p < 0.01). These data may be interpreted to m ean that the endometrium has the ability to distinguish between closel y related Type I IFNs.