Abstract
Interferon tau (IFNtau) is the antiluteolytic signal produced by the conceptus of ruminants. Intrauterine administration of recombinant ovine IFNtau suppresses expression of endometrial estrogen receptor (ER) and oxytocin receptor (OTR) in the luminal and superficial glandular epithelia to abrogate the production of luteolytic prostaglandin F(2alpha) (PGF(2alpha)) pulses. Subcutaneous (s.c.) injections of recombinant ovine (o) IFNtau appear to extend the interestrous interval by altering uterine PGF(2alpha) response to oxytocin. The present study tested the hypothesis that antiluteolytic effects of roIFNtau injected into the uterine lumen (paracrine) or s.c. (endocrine) are equivalent in suppressing expression of endometrial ER and OTR and inducing uterine expression of type I IFN-regulated Mx and ubiquitin cross-reactive proteins (UCRP). Sixteen cyclic ewes were fitted with uterine catheters on Day 5 (Day 0 = estrus), were assigned randomly to receive treatment with control proteins or roIFNtau (2 x 10(7) antiviral units/day) by either intrauterine or s.c. injections from Days 11 to 15, and were ovariohysterectomized on Day 16. Results indicated that expression of ER and OTR mRNAs in endometrial epithelium was suppressed by intrauterine but not by s.c. injections of roIFNtau. Intrauterine injections of roIFNtau increased expression of Mx and UCRP mRNA in the endometrium. Subcutaneous injections of roIFNtau increased endometrial Mx mRNA levels but not UCRP mRNA. Unexpectedly, intrauterine and s.c. injections of roIFNtau were equally effective in inducing expression of Mx and UCRP mRNA in the corpus luteum. Although s.c. injections of roIFNtau induced Mx mRNA in the endometrial epithelium, s.c. injections of roIFNtau did not abrogate activation of the uterine luteolytic mechanism by suppressing epithelial ER and OTR expression. Therefore, results of this study failed to support the assumption that endocrine roIFNtau mimics antiluteolytic effects of paracrine IFNtau to improve pregnancy rates in sheep.
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