Bioscientifica Proceedings

Enhanced secretion of PGF_2α from endometrial explants in vitro in response to oxytocin is associated with augmented activities of phospholipase A₂, phospholipase C and prostaglandin endoperoxide H synthase (PGS). In early pregnancy, maintenance of the corpus luteum is associated with an absence of pulsatile PGF_2α secretion; an increase in endometrial inhibitors of phospholipase A₂ and PGS contribute to the antiluteolytic alterations of PGF_2α secretion. Linoleic acid is a competitive inhibitor of arachidonic acid metabolism by PGS, and microsomal concentrations of free linoleic acid are increased in the endometrium of pregnant cattle. The trophoblast produces large quantities of interferon tau (IFN-τ). Inhibition of increases in endometrial oestradiol receptor mRNA and protein are associated with intrauterine administration of recombinant (r) ovine (o) IFN-τ in sheep. Intrauterine injections of rbovine (b) IFN-τ in cattle (days 14–17) altered endometrial function so that secretion of PGF_2α from cultured endometrial epithelial cells was reduced. Antiluteolytic effects were not expressed in 20% of cows receiving IFN-τ or rbIFN-α_I1 indicating that an inadequate endometrial responsiveness may contribute to embryo mortality. IFN-τ may activate a signal transduction system similar to that induced by other type I IFNs; activation of an intracellular tyrosine kinase ultimately leads to activation of an IFN-stimulated response element to induce gene transcription. Biological responses associated with pregnancy and IFN-τ treatment are integrated into a multifactorial antiluteolytic model. Strategies to enhance embryo survival could include supplementation with rIFN-τ and alterations in endometrial responsiveness to this cytokine through dietary manipulation of lipid metabolism.

© 1995 Journals of Reproduction and Fertility Ltd