Proceedings of The Physiological Society

King's College London (2008) Proc Physiol Soc 13, PC27

Poster Communications

Cholesterol depletion alters coronary artery myocyte Ca2+ signalling in an agonist-specific manner

C. Prendergast1, J. Quayle2, T. Burdyga1, S. Wray1

1. Department of Physiology, University of Liverpool, Liverpool, United Kingdom. 2. Human Anatomy and Cell Biology, University of Liverpool, Liverpool, United Kingdom.

Caveolae, flask-like invaginations of the cell membrane stabilised by caveolin proteins and rich in cholesterol, are abundant in vascular smooth muscle. Depletion of cell membrane cholesterol disrupts caveolae and may lead to alterations in cell signalling. Given the importance of the coronary arteries to health and the association of hypercholesterolemia with atherosclerosis, endothelial dysfunction and impaired vascular smooth muscle function, it is of interest and significance to determine the effect of cholesterol manipulation in this vessel. We have examined the effects of methylcyclodextrin (MCD), a cholesterol depleting agent, on agonist-induced in situ [Ca2+]i signalling in rat coronary artery myocytes from an intact preparation, using confocal microscopy. N numbers varied from 14 to 30 cells, from a minimum of 3 animals. Incubation with MCD led to the significant and selective reduction of the response to 5-HT (10μM; 76.3±5%) and endothelin-1 (10nM; 86.6±4%), while the response to phenylephrine (100μM) remained unchanged. These data were confirmed using cholesterol oxidase as the cholesterol depleting agent. When cholesterol was replenished, using cholesterol-saturated MCD, Ca2+ signalling was restored. The response to high K+ (60mM) and caffeine (10mM; under both normal and Ca2+-free conditions) was unaffected by MCD. In additional experiments, enzymatically isolated myocytes were patch clamped. MCD induced a large increase in whole cell outward K+ current and a significant decrease in cell capacitance. Modulation of cell membrane cholesterol altered coronary artery myocyte Ca2+ signalling in an agonist-specific manner, indicating the importance of caveolae in the maintenance of myocyte signalling processes.

Where applicable, experiments conform with Society ethical requirements