Effects of tumor necrosis factor-α and nitric oxide on prostaglandins secretion by the bovine oviduct differ in the isthmus and ampulla and depend on the phase of the estrous cycle

To determine the possible roles of tumor necrosis factor-α (TNFα) and nitric oxide (NO) in the bovine oviduct, ampulla and isthmus collected during the estrous cycle were exposed for 18 h to TNFα, NO donor (NONOate), NO synthase inhibitors (L-NOARG, L-NAME and AMT) and oxytocin (OT) as a positive control. Prostaglandins (PGs) and NO₂/NO₃ in conditioned media were measured. TNFα stimulated PGF_2α secretion on Day 0 (onset of estrus = Day 0) and Days 2-3, in both the ampulla and isthmus, but on Days 18-20 only in ampulla. TNFα increased PGE ₂ secretion in both fragments in each phase. NONOate did not affect PGF_2α secretion on Days 18-20, whereas this NO donor stimulated PGF_2α secretion in both fragments on Day 0 and Days 2-3. TNFα increased NO₂/NO₃ production in every examined phase in the ampulla and on Days 2-3 in the isthmus. L-NAME lowered NO ₂/NO₃ production regardless of phase or fragment. L-NOARG and AMT lowered NO₂/NO₃ production in both fragments on Day 0 and Days 2-3. The possible role of TNFα, NO or PGs on the oviductal contractility during the early-luteal phase was also examined. Neither TNFα nor NONOate influenced contractility in either fragment. Although PGF_2α stimulated the contraction in both fragments, PGE ₂ decreased it. When taken together, TNFα seems to play some role as a modulator of PGF_2α and PGE₂ production and for transferring the embryo from the oviduct to the uterus by stimulating NO production in the bovine oviduct.