in vascular smooth muscle both alpha 1- and alpha 2-adrenoceptors exist postjunctionally , the alpha 1 subtype being innervated preferentially in most vascular beds . alpha 2-adrenoceptors may be present on the smooth muscle cell as well as the endothelial cell where they may participate in the release of endothelium derived relaxing and constricting factors .
C0225336
endothelial cell
C0014257
endothelium