Effects of indomethacin on human placental stem villous arteries

Ring preparations of human stem villous arteries were prepared by microtechnique from placentae born after normal-term vaginal delivery. Isometric tension was recorded in organ baths. Indomethacin 10(-8)-10(-5) M left responses to K+ depolarization and contractions produced by prostaglandin F2 alpha (PGF2 alpha) unaffected, while indomethacin 10(-4) M slightly decreased K+-induced contractions and inhibited responses to PGF2 alpha. In contrast, nitrendipine 10(-9)-10(-6) M markedly decreased responses to K+ while nitrendipine 10(-8)-10(-6) M inhibited PGF2 alpha-induced responses. Relaxant responses to vasointestinal polypeptide 10(-8)-10(-7)M were left unaffected by pretreatment with indomethacin 5 X 10(-5) M. Indomethacin affects contractile activation in human stem villous arteries only in high concentrations, and the effects differ in profile from those of calcium entry blockers like nitrendipine. The results do not leave evidence for increased placental arterial tone during indomethacin treatment in pregnancy.