AJP - Cell Physiology, Vol 264, Issue 1 C32-C39, Copyright © 1993 by American Physiological Society

ARTICLES

Acute exposure to cholesterol increases arterial nitroprusside- and endothelium-mediated relaxation

R. A. Bialecki and T. N. Tulenko
Department of Physiology and Biochemistry, Medical College of Pennsylvania, Philadelphia 19129.

The effect of cholesterol enrichment on arterial relaxation was studied by evaluating sodium nitroprusside (SNP)- and endothelium-mediated relaxation of isolated rabbit carotid artery. Arterial segments were perfused in vitro (4 h) with cholesterol-rich liposomes consisting of free cholesterol (FC) and phospholipid (PL) in a 2:1 molar ratio. Ring segments from arteries exposed to cholesterol-rich liposomes exhibited a 60% increase (P < 0.01) in FC content without affecting PL content. Cholesterol-enrichment was associated with a twofold increase (r = 0.92, P < 0.05) in acetylcholine- and A23187-induced endothelium-mediated relaxation. Bioassay of endothelium-derived relaxing factor(s) (EDRF) after cholesterol exposure indicated that EDRF half-life and/or release increased (P < 0.05) threefold. A trend (P = 0.07) toward increased smooth muscle cell sensitivity to EDRF after cholesterol enrichment was also observed. Cholesterol enrichment increased (P < 0.05) sensitivity to SNP 12-fold, and this difference was further augmented (P < 0.01) twofold with endothelium removal. Cholesterol enrichment had no effect on relaxation to N2,2'-O-dibutyrylguanosine 3',5'-cyclic monophosphate. These data indicate that acute cholesterol enrichment increases EDRF activity from arterial endothelium and increases smooth muscle responses to both EDRF and SNP.

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