The dialogue between trophectoderm cells of the conceptus and epithelial cells of the endometrium is critical to CL maintenance and embryo survival. The signal transduction mechanisms by which bovine interferon (IFN)-τ regulates cyclooxygenase (COX)-2 expression and secretion of prostaglandin F_2α (PGF_2α) in bovine endometrial (BEND) cells is being examined. Stimulation of Protein Kinase C with a phorbol ester (phorbol 12, 13 dibutyrate [PDBu]) activates COX-2 gene expression and PGF2_α secretion via the mitogen-activated protein kinase (MAPK) pathway. Interferon-τ attenuates PDBu activation of PGF_2α secretion, but this inhibitory effect appears to be independent of the MAPK pathway. Embryonic IFN-τ, acting through a Type I IFN receptor, activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway resulting in activation or repression of interferon-stimulated genes. Experimental evidence is provided that IFN-τ regulation of STATs regulates gene expression of COX-2 in a manner that decreases secretion of PGF_2α in the immortalized bovine endometrial cells (BEND Cells). Maternal regulation of the antiluteolytic pathway is under investigation relative to the ability of the polyunsaturated fatty acid, eicosapentaenoic (EPA), to decrease endometrial secretion of PGF_2α and progesterone to increase both conceptus development and IFN-τ secretion.

Evidence is presented that bST (bovine somatotrophin) treatment of lactating dairy cows will enhance both expression of oviductal IGF(Insulin-Like Growth Factor)-II mRNA and endometrial IGFBP (Insulin-Like Growth Factor Binding Protein)-3 mRNA between day 3-7 of the oestrous cycle. The mRNA for GH receptor increased in endometrial tissues between days 3 and 7. These bST-induced changes may contribute to stimulation in embryo development and pregnancy rates in lactating dairy cows. Additive effects of bST and rbIFN-τ, to inhibit phorbol ester induction of PGF_α secretion in immortalized bovine endometrial cells, indicates interplay between their signal transduction pathways. Non-lactating dairy cows were slaughtered at day 17 after oestrus to evaluate effects of pregnancy status (cyclic vs. pregnant) and bST (bST vs control) injections on endometrial gene expression. Distinctly different mRNA and protein responses were detected between cyclic and pregnant cows related to luteolytic-antiluteolytic drive (i.e., expression of PR [Progesterone Receptor], OTR [Oxytocin Receptor], ER [Estradiol Receptor]-α, PGHS [Prostaglandin GH Synthase]-2, PGFS [Prostaglandin F Synthase], PGES [Prostaglandin E Synthase]). BST induced changes in PGHS2 protein (+), OTR mRNA (-) and ERa protein (+) may potentially impact on the mechanisms associated with maintenance of pregnancy. Basic studies of this nature provide the framework for development of reproductive management systems to improve reproductive efficiency of the dairy herd.