In vivo microvascular vasodilator responses to acetylcholine are increased in women with pre-eclampsia, while endothelial-independent vasodilation is unchanged. Although the mechanism of acetylcholine induced vasodilation in small vessels is unclear, this study confirms previous animal data and provides in vivo evidence of altered microvascular endothelial cell function in pre-eclampsia.

Objectives To evaluate in vivo microvascular responses to incremental doses of the endothelial-dependent vasodilator, acetylcholine, and the endothelial-independent vasodilator, sodium nitroprusside, in women with pre-eclampsia and gestation-matched normotensive pregnant controls. Design Prospective clinical study.Setting Southern Derbyshire Acute Hospitals Trust, and University of Nottingham Division of Vascular Medicine.Population Thirteen women with pre-eclampsia and 16 normotensive pregnant controls.Methods Cutaneous microvascular vasodilator responses to iontophoretic administration of incremental doses of acetylcholine and sodium nitroprusside (25-100mC) were evaluated under temperature-controlled conditions using laser Doppler¯uximetry. ResultsResting skin temperature and blood¯ow were similar among 13 women with pre-eclampsia [mean blood pressure 151/93 mmHg (4/3); mean gestation 35.6 weeks (1.0); and mean proteinuria 1.1 g/24h (0.2)] and 16 normotensive pregnant controls [mean blood pressure 111/63 mmHg (2/2); mean gestation 34.3 weeks (0.9)]. Peak vasodilator responses to acetylcholine were increased in women with pre-eclampsia (median¯ux ratio 15.1 [IQR 12.3-17.6] vs 11.7 [IQR 8.4-12.6], P , 0.05), whereas sodium nitroprusside responses were not different between the two groups: 11.4 [IQR 8.6-13.4] vs 9.5 [IQR 8.0-12.3].Conclusion In vivo microvascular vasodilator responses to acetylcholine are increased in women with preeclampsia, while endothelial-independent vasodilation is unchanged. Although the mechanism of acetylcholine induced vasodilation in small vessels is unclear, this study con®rms previous animal data and provides in vivo evidence of altered microvascular endothelial cell function in pre-eclampsia.

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