Effects of bTP-1 and oxytocin on prostaglandin and protein production by the bovine endometrium

There is evidence that conceptal proteins in general, and bovine trophoblast protein-1 (bTP-1) specifically, alter biochemical mechanisms which are responsible for returning cattle to estrus. Endometrial explants, gland fragments, glandular epithelial cells, and stromal cells from uteri of cyclic cows (N=4) were cultured in medium containing 1 ug/ml bovine serum albumen (BSA), 1 ug bovine trophoblast protein-1 (bTP-1), 50 mU oxytocin after 8 h, or 1 ug/ml bTP-1 followed by 50 mU oxytocin at 8 h and examined their effects on prostaglandin and protein secretion. Explants treated with bTP-1 secreted less Prostaglandin F₂α (PGF₂α) than explants receiving BSA (P<0.05) or oxytocin alone (P<0.001). Oxytocin treated tissue or cells secreted significantly more PGF₂α than bTP-1 treatments (P<0.05) and BSA treatments (P<0.05) in all cultures. Glandular epithelial cell cultures treated with oxytocin secreted more prostaglandin E₂ (P, 0.05) than cultures treated with BSA or bTP-1. Glandular epithelial cells produced more PGF₂α than any other group when normalized to total cellular protein, while stromal cells produced more PGE₂. There was no effect of treatment on incorporation of radiolabeled methionine and cysteine into macromolecules although stromal cells incorporated more radiolabel than other cell or tissue type. Two-dimensional-SDS PAGE and fluorography revealed that similar proteins were secreted by explants, glandular epithelial cells, and intact gland fragments but no differences were observed due to treatment. These results indicate bTP-1 and/or oxytocin affect prostaglandin secretion in in vitro models of the bovine endometrium in manner that helps explain in vivo observations.