In vitro perfusion studies of human resistance artery function in essential hypertension

To simulate in vivo conditions as closely as possible to in vitro conditions, we examined the morphological and functional characteristics of isolated human subcutaneous small arteries from 17 essential hypertensive patients and 14 normotensive control subjects using a perfusion myograph. Vessel segments were cannulated and exposed to conditions of constant flow and pressure. The ratio of media thickness to lumen diameter in arteries from hypertensive patients increased significantly. With the endothelium intact, sensitivity to extraluminally applied norepinephrine was not different, and this was not affected by inhibition of neuronal amine uptake with cocaine. After removal of the endothelium, sensitivity to norepinephrine was augmented in normotensive vessels to a greater extent than in hypertensive vessels. Endothelium-dependent relaxation to acetylcholine was significantly reduced in arteries from hypertensive patients, but endothelium-independent relaxation to sodium nitroprusside was not different from that observed in vessels from normotensive control subjects. These data demonstrate that sensitivity to exogenous norepinephrine is not different in essential hypertension but that there is defective endothelium-dependent dilatation, suggesting a contributory role for endothelium dysfunction in human essential hypertension.