EXPRESSION OF ALPHA(2)-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 w hich 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 pr obes in in situ hybridization and RNase protection assays to analyze t he expression of alpha(2)-AR in the thoracic aorta of New Zealand Whit e (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbits, a model for atherosclerosis. We found that the alpha(2A)-AR mRNA was in endoth elial and smooth muscle cells in both NZW and WHHL aorta. In addition, the shoulders and subendothelial regions of the atherosclerotic lesio ns in WHHL aorta showed abundant expression of alpha(2A)-AR mRNA, Anti bodies to macrophage (RAM-11) and smooth muscle cell (HHF-35) antigens were used to localize macrophage and smooth muscle cells in aortic se ctions from WHHL rabbits. The expression of alpha(2A)-AR mRNA within t he lesions of WHHL rabbits correlated with the presence of infiltratin g macrophages. We discuss the potential role of alpha(2A)-ARs in macro phage function and in promoting atherosclerosis.