Affiliation:
1. From the Department of Physiological Sciences (K.D., P.H., K.S.), Lund University, Lund, Sweden, and the Department of Medical Physiology (M.V., J.V.) and the Department of Medical Anatomy (J.T.-J.), Panum Institute, University of Copenhagen, Copenhagen, Denmark.
Abstract
Objective—
This study assessed the role of cholesterol-rich membrane regions, including caveolae, in the regulation of arterial contractility.
Methods and Results—
Rat tail artery devoid of endothelium was treated with the cholesterol acceptor methyl-β-cyclodextrin, and the effects on force and Ca
2+
handling were evaluated. In cholesterol-depleted preparations, the force responses to α
1
-adrenergic receptors, membrane depolarization, inhibition of myosin light chain phosphatase, and activation of G proteins with a mixture of 20 mmol/L NaF and 60 μmol/L AlCl
3
were unaffected. In contrast, responses to 5-hydroxytryptamine (5-HT), vasopressin, and endothelin were reduced by >50%. The rise in global intracellular free Ca
2+
concentration in response to 5-HT was attenuated, as was the generation of Ca
2+
waves at the cellular level. By electron microscopy, cholesterol depletion was found to disrupt caveolae. The 5-HT response could be restored by exogenous cholesterol, which also restored caveolae. Western blots showed that the levels of 5-HT
2A
receptor and of caveolin-1 were unaffected by cholesterol extraction. Sucrose gradient centrifugation showed enrichment of 5-HT
2A
receptors, but not α
1
-adrenergic receptors, in the caveolin-1–containing fractions, suggesting localization of the former to caveolae.
Conclusions—
These results show that a subset of signaling pathways that regulate smooth muscle contraction depends specifically on cholesterol. Furthermore, the cholesterol-dependent step in serotonergic signaling occurs early in the pathway and depends on the integrity of caveolae.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine
Cited by
158 articles.
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