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1 Department of Animal Sciences, University of Florida, Gainesville 32611-0910
2 Department of Biochemistry, Faculty of Veterinary Medicine, University of Uruguay, Montevideo, Uruguay
3 Department of Veterinary Medicine, Faculty of Agriculture, Kagoshima University, Kagoshima, Japan
4 College of Agriculture, Dept. Animal Production, Universidad Centroccidental Lisandro Alvarado, Barquisimeto, Lara, Venezuela
5 Department of Plant and Animal Sciences, Nova Scotia Agricultural College, Truro, Canada
Corresponding author: William W. Thatcher; e-mail: thatcher{at}animal.ufl.edu.
The objective was to evaluate the effects of pregnancy and bovine somatotropin (bST) on endometrial gene and protein expression related to maintenance of pregnancy in nonlactating dairy cows at d 17. In endometrial tissues, treatment with bST increased the steady state concentration of oxytocin receptor (OTR) mRNA; bST-treated cyclic (bST-C) cows had greater OTR mRNA than bST-treated pregnant (bST-P) cows. Estradiol receptor 
(ER) mRNA was reduced in bST-P cows compared with control P and C (no bST) cows. Western blotting revealed that pregnancy decreased the abundance of ER protein, and bST stimulated an increase in ER protein in C and P cows. Treatment with bST increased steady state concentrations of progesterone receptor (PR) mRNA. No differences were detected in steady state mRNA concentrations of prostaglandin H synthase-2 (PGHS-2), prostaglandin E synthase, and prostaglandin F synthase due to pregnancy or bST treatment. However, PGHS-2 protein was increased in response to pregnancy and bST treatment. Immunostaining indicated that P decreased ER protein in luminal epithelium and increased PR protein in epithelial cells of the uterine glands. The PR protein response in the glands was less in bST-P cows than in P cows. In the stromal layer of the endometrium, bST decreased PR protein abundance in C and P cows. The PGHS-2 protein was localized exclusively in the luminal epithelium cells of endometrium and was increased in P cows. In conclusion, distinctly different mRNA and protein responses were detected between C and P cows related to prostaglandin biosynthesis, and bST-induced changes may potentially impact mechanisms associated with maintenance of pregnancy in nonlactating cows.
Key Words: pregnancy • bovine somatotropin • endometrium
Abbreviation key: C = cyclic, CL = corpus luteum, ER = estradiol receptor , IFN-
= interferon-, OTR = oxytocin receptor, P = pregnant, PG = prostaglandin, PGES = prostaglandin E synthase, PGFM = 13, 14-dihydro 15-keto PGF2, PGFS = prostaglandin F synthase, PGHS-2 = prostaglandin H synthase-2, PR = progesterone receptor.
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