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

Summary. The prostaglandins PGE₁, PGE ₂, PGD ₂, PGF _2α., U46619 and 6_β-PGI_l 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. PGF_2α, 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 6_β-PG1₁, caused significant, dose-related attenuations of the angiotensin II vasoconstrictive response whereas PGE₂, PGF_2α, 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.