Expression of α2-adrenergic receptors in normal and atherosclerotic rabbit aorta

alpha(2)-Adrenergic receptors (alpha(2)-ARs) in vascular smooth muscle cells are known to mediate vasoconstriction; however, it is unknown which of the 3 subtypes of alpha(2)-AR (alpha(2A), alpha(2B), or alpha(2C)) is expressed in vascular tissue. We have used subtype-specific probes in in situ hybridization and RNase protection assays to analyze the expression of alpha(2)-AR in the thoracic aorta of New Zealand White (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbits, a model for atherosclerosis. We found that the alpha(2A)-AR mRNA was in endothelial and smooth muscle cells in both NZW and WHHL aorta. In addition, the shoulders and subendothelial regions of the atherosclerotic lesions in WHHL aorta showed abundant expression of alpha(2A)-AR mRNA, Antibodies to macrophage (RAM-11) and smooth muscle cell (HHF-35) antigens were used to localize macrophage and smooth muscle cells in aortic sections from WHHL rabbits. The expression of alpha(2A)-AR mRNA within the lesions of WHHL rabbits correlated with the presence of infiltrating macrophages. We discuss the potential role of alpha(2A)-ARs in macrophage function and in promoting atherosclerosis.