Comparison of the vasoactive effects of leukotrienes with thromboxane mimic in the perfused human placenta

Vasoactive effects of leukotrienes and thromboxane mimic were tested in the perfused human placental cotyledon. Tissue viability was demonstrated by oxygen consumption and by carbon dioxide and lactate production. Vasoconstrictive effects of leukotrienes B4, C4, and D4 were compared with those of a known potent vasoconstrictor, thromboxane mimic (U 46619). The leukotrienes and thromboxane mimic were administered as bolus injections into a chorionic plate artery in doses ranging from 10(-6) to 25 micrograms. In each placenta only one leukotriene was compared with thromboxane mimic. Vasoconstrictive effects were determined by maximum increases in resistance occurring after each injection. Thromboxane mimic caused significantly greater increases in resistance than any of the leukotrienes (p less than 0.001). Thromboxane mimic and leukotriene D4 had significantly lower threshold doses than leukotriene B4 or C4 (p less than 0.001). We concluded: (1) Thromboxane mimic is a potent vasoconstrictor in the human placental vasculature; (2) leukotrienes also cause vasoconstriction but are much less potent than thromboxane; (3) thromboxane mimic and leukotriene D4 have vasoconstrictor effects at significantly lower (p less than 0.001) concentrations than leukotriene B4 or C4.