Effects of the estrous cycle, pregnancy, and interferon tau on 2 ',5 '-oligoadenylate synthetase expression in the ovine uterus

The enzymes which comprise the 2',5'-oligoadenylate synthetase (OAS) family are interferon (IFN) stimulated genes which regulate ribonuclease L antivi ral responses and may play additional roles in control of cellular growth a nd differentiation. This study characterized OAS expression in the endometr ium of cyclic and pregnant ewes as well as determined effects of IFN tau an d progesterone on OAS expression in cyclic or ovariectomized ewes and in en dometrial epithelial and stromal cell lines. In cyclic ewes, low levels of OAS protein were detected in the endometrial stroma (S) and glandular epith elium (CE). In early pregnant ewes, OAS expression increased in the S and G E on Day 15. OAS expression in the lumenal epithelium (LE) was not detected in uteri from either cyclic or pregnant ewes. Intrauterine administration of IFN tau stimulated OAS expression in the S and CE, and this effect of IF N tau was dependent on progesterone. Ovine endometrial LE, GE, and S cell l ines responded to IFN tau with induction of OAS proteins. In all three cell lines, the 40/46-kDa OAS forms were induced by IFN tau, whereas the 100-kD a OAS form appeared to be constitutively expressed and not affected by IFN tau. The 69/71-kDa OAS forms were induced by IFN tau in the S and GE cell l ines, but not in the LE. Collectively, these results indicate that OAS expr ession in the endometrial S and CE of the early pregnant ovine uterus is di rectly regulated by IFN tau from conceptus and requires the presence of pro gesterone.