PARENT SESSION
BIOLOGY OF THE FEMALE REPRODUCTIVE TRACT
Harborside C
7:30 AM-10:00 AM

(532) EFFECTS OF PREGNANCY AND BOVINE SOMATOTROPHIN (bST) ON ENDOMETRIAL ESTROGEN RECEPTOR- (ER-), PGHS2, AND PGF₂ SECRETION ON DAY 17 AFTER ESTRUS IN NONLACTATING DAIRY COWS.

Guzeloglu, Aydin¹, Bilby, Todd¹, Kamimura, Shunichi¹, Meikle, Ana², Badinga, Lokenga¹, Dinges, Amanda¹, Hernandez, Oscar¹, Thatcher, William¹, ¹ Department of Animal Sciences, University of Florida, Gainesville, FL² Department of Biochemistry, Veterinary Faculty, Montevideo, Uruguay

ABSTRACT- Cows were either inseminated (n=31) or not (cyclic, n=14) to a timed ovulation (d0). In a 2x2 factorial design, cows received either bST (n=28; d0 and d11, 500 mg, Posilac, Monsanto Co.) or no bST (n=17). On day 17, cows were slaughtered and uteri flushed to recover secretions and conceptus. Endometrial tissues were collected from the ipsilateral horn to the CL for protein and mRNA analyses. Pregnant cows (n=10) had higher PGF₂ in uterine flushings (619 ±95 >109 ±51 ng; P<0.01). In 22 cows (cyclic [n=5], pregnant [n=6], cyclic-bST [n=7] and pregnant-bST [n=4]) ER and PGHS2 protein, ER mRNA, and immunohistochemical-spatial-localization of ER were quantified. Pregnancy decreased expression of ER in luminal epithelium (P <0.02). Heavy staining for the ER was detected in deep endometrial glands (P <0.01) compared to superficial and medium glands irrespective of bST and pregnancy statuses. Pregnancy decreased endometrial ER mRNA (0.421 ±0.05 <0.602 ±0.046 fmol/mg Total Nucleic Acid; P <0.02) with no effect of bST. A differential response of ER protein was detected due to pregnancy decrease (P<0.01) and bST stimulation (P<0.01). Expression of PGHS2 protein was stimulated both by pregnancy (P <0.01) and bST (P<0.05). In a sub-sample of 7 cyclic cows, endometrial epithelial cells were isolated from the uterine horn contralateral to the ovary bearing the CL and cultured in a serum-free DMEM/F12 media until 90 % confluent. Cells were treated in a factorial design with IFN-(0, 50 or 500 ng/ml) and phorbol 12,13 dibutyrate (PdBu: 0 or 100 ng /ml) with media collected after 24 hours for PGF₂. Treatment with PdBu induced PGF₂ secretion (P <0.01), and IFN- caused a 26% reduction in PGF₂ secretion induced by PdBu (P <0.01). Secretion of PGE₂ was lower than PGF₂ (PGE₂ /PGF₂ <1). Both PdBu (P<0.01) and IFN- (P<0.01) induced secretion of PGE₂ . In summary, pregnancy reduces mRNA expression of ER and increased PGHS2 protein. Cross talk between pregnancy (i.e., IFN-) and bST may lead to stimulation in ER and PGHS2 protein. Attenuation of luteolytic PGF₂ secretion during pregnancy or in response to IFN- appears to be on regulating either PGHS2 activity or downstream differential metabolism of PGH.

KEY WORDS: Uterus, bST, ER, PGF₂