The actions of prostaglandins and their interactions with angiotensin II in the isolated perfused human placental cotyledon

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Abstract
Summary. The prostaglandins PGE1, PGE 2, PGD 2, PGF 2α., U46619 and 6β‐PGIl were administered as bolus injections both separately and in combination with angiotensin II into the fetal circulation of isolated human placental cotyledons perfused in vitro. PGF2α, and PGD2, caused small dosedependent increases in fetal perfusion pressure when compared with U46619 which acted as an extremely potent vasoconstrictor of the fetal‐placental vasculature. PGE1, caused very small dose‐dependent decreases in fetal perfusion pressure when injected on its own. In combination with angiotensin 11, PGE1, PGD2, and 6β‐PG11, caused significant, dose‐related attenuations of the angiotensin II vasoconstrictive response whereas PGE2, PGF2α, and U46619 potentiated the response. Injections of angiotensin II after the infusion of indomethacin into the fetal circulation resulted in a potentiation of angiotensin II induced vasoconstriction. The results indicate that prostaglandins exert their effects on the fetal‐placental circulation by modulating the actions of angiotensin II.