Endothelium-dependent relaxation is unaltered by hypertension, cholesterol or intimal thickening

The effect of cellophane wrap hypertension (WRAP) and hypercholesterolemia (1% cholesterol diet, CHOL) for 4 weeks was assessed on the endothelium-dependent vasodilator response to acetylcholine in conscious rabbits after pharmacological autonomic blockade. Dose-response curves for the hindlimb vascular resistance (ear artery pressure/lower aortic blood flow; Doppler flowmeter) and acetylcholine infusion (i.v.) doses were unaltered in sensitivity (ED50) for any of the treatment groups. The range and slope of the curves were significantly altered by WRAP, CHOL or WRAP plus CHOL for acetylcholine and adenosine infusions consistent with medial hypertrophy in resistance vessels and raised serum viscosity. The effect of intimal thickening on the response to endothelium derived relaxing factor (EDRF) was tested in dog carotid artery ring segments in vitro 4 weeks after endothelium removal. The relaxation responses to acetylcholine (EDRF-dependent) and adenosine or nitroglycerin were not significantly altered by the neo-intima. Therefore the response to EDRF released by acetylcholine in resistance vessels was unaltered by hypertension, hypercholesterolemia or both together. Neo-intimal thickening in response to initial endothelium loss does not appear to alter EDRF responses in the carotid artery.