MYOGENIC AND ENDOTHELIAL PROPERTIES OF MYOMETRIAL RESISTANCE ARTERIESFROM WOMEN WITH PREECLAMPSIA

Objective: To compare myometrial resistance arteries from women with p reeclampsia and normal pregnant women with respect to myogenic behavio r, acetylcholine-mediated dilatation, and distensibility. Study Design : Arteries from women with preeclampsia (n = 14) and healthy term preg nant women (n = 17) were studied in a pressurized arteriograph system. Myogenic tone was evaluated during increments in intraluminal pressur e from 20 to 120 mm Hg, as well as distensibility index at the same pr essure steps in Ca2+-free solution substituted with papaverine. Endoth elium-dependent relaxation was assessed by evaluating the response to acetylcholine (10(-6) M) in the absence and presence of N-omega-nitro- L-arginine in arteries pressurized at a constant intraluminal pressure of 70 mm Hg. Results: Overall myogenic tone did not differ between th e arteries from the two patient groups studied, but the slope of the p ressure-myogenic tone relationship in arteries from women with preecla mpsia was significantly different (positive). Relaxation to acetylchol ine was impaired in arteries from women with preeclampsia (6 +/- 1% ve rsus 18 +/- 4%, p < 0.05), whereas inhibition of nitric oxide synthase with NO-nitro-L-arginine abolished this response in both patients gro ups. The distensibility index (Ca2+-free solution plus papaverine) of arteries from women with preeclampsia was increased as compared to art eries from normal pregnant women (p < 0.05). Conclusions: Pressure-ind uced myogenic tone and impaired acetylcholine-mediated vasodilatation in myometrial resistance arteries from women with preeclampsia might c ontribute to the increased vascular resistance in the uterine circulat ion seen in preeclampsia. The increased distensibility of the myometri al arteries from women with preeclampsia might represent a compensator y mechanism to preserve the blood flow in the uteroplacental vascular bed.