Expression of multiple alpha(1)-adrenoceptors on vascular smooth muscle: Correlation with the regulation of contraction

Previous work has shown that the genes encoding each a,adrenoceptor subtype are coexpressed throughout the peripheral vascular system. We have evaluat ed subtype-selective antibodies as tools to determine the extent of protein expression in arteries. The alpha(1A)-, alpha(1B)-, and alpha(1D)-adrenoce ptors were detected in the medial layer of the aorta, caudal, femoral, ilia c, renal, superior mesenteric, and mesenteric resistance arteries. In Rat1 fibroblasts expressing each subtype, immunoreactivity was noted both on the cell surface and in a perinuclear orientation. Intense a,,-adrenoceptor im munostaining was similarly localized in cultured femoral and renal vascular smooth muscle cells. Although the cellular localization appeared to be the same, immunoreactivity obtained with alpha(1A)- and alpha(1D)-adrenoceptor s was much less intense than that with the alpha(1B)-adrenoceptor. The alph a(1A)-adrenoceptor selective agonist A-61603 was 22-fold more potent in act ivating renal artery contraction when compared with the femoral artery. The expression of each a,-adrenoceptor was significantly decreased by in vivo application of antisense oligonucleotides targeted against each subtype. In hibition of the expression of only one, the alpha(1A) in renal and the alph a(1D) in femoral arteries, reduced the contractile response to naphazoline. The results show: 1) subtype-selective antibodies can be used in tissues a nd cell culture to localize the alpha(1)-adrenoceptor subtypes, 2) in addit ion to expression on the cell surface, the alpha(1)-adrenoceptors are expre ssed intracellularly, and 3) despite expression of all adrenoceptors, a sin gle subtype mediates the contractile response in the femoral and renal arte ries.