THE FETOPLACENTAL PRESSOR EFFECTS OF LOW-DOSE ACETYLSALICYLIC-ACID AND ANGIOTENSIN-II IN THE EX-VIVO COTYLEDON MODEL

OBJECTIVE: Our purpose was to investigate perfusion pressure changes e x vivo induced by angiotensin II on fetoplacental vasculature pretreat ed with low-dose acetylsalicylic acid. STUDY DESIGN: Two cotyledons fr om each of 12 placentas were perfused. The intervillous space of one c otyledon was infused with acetylsalicylic acid (5 x 10(-5) mol/L) simi lar to the serum concentration of women receiving daily low-dose aspir in therapy (60 to 81 mg). The control cotyledon was infused with an eq uivalent amount of normal saline solution. Two doses of angiotensin II , 1 x 10(-11.5) and 1 x 10(-10) moles, were injected as boluses into t he chorionic arteries of each cotyledon. A 3 x 10(-7) mole dose of ang iotensin II was also injected into the intervillous space. Statistical analysis was performed with analysis of variance, and results are exp ressed as mean pressure change in millimeters of mercury +/- SEM. RESU LTS: Perfusion pressure response did not vary between cotyledons pretr eated with acetylsalicylic acid and control cotyledons when 3 x 10(-7) moles of angiotensin II was injected into the intervillous space (8.0 +/- 1.9 mm Hg vs 9.8 +/- 1.6 mm Hg, p = 0.59). There were no differen ces between cotyledons in pressure response to 1 x 10(-11.5) moles of angiotensin II injected into the fetal circuit (5.9 +/- 0.8 mm Hg vs 6 .7 +/- 0.9 mm Hg, p = 0.51). However, in the cotyledons pretreated wit h acetylsalicylic acid there was a decrease in the presser response to 1 x 10(-10) moles of angiotensin II (14.1 +/- 1.4 mm Hg vs 21.5 +/- 3 .3 mm Hg, p = 0.05). CONCLUSIONS: Low-dose aspirin infused into the in tervillous space decreases vasoconstriction elicited by angiotensin II in the fetoplacental compartment. This suggests that maternal low-dos e aspirin therapy has effects in the fetoplacental circulation in addi tion to its effects in the maternal circulation.