Purinergic receptor distribution in endothelial cells in blood vessels: a basis for selection of coronary artery grafts

Expression levels of the purinergic P2X receptor subunits (P2X1 to P2X7) and P2Y2 were examined in the endothelial cell layer of internal mammary artery (Ann. Thorac. Surg. 54 (1992) 652), radial artery (Ann. Thorac. Surg. 16 (1973) 111) and saphenous vein (Ann. Thorac. Surg. 20 (1975) 628) samples obtained at surgery for coronary artery bypass grafts using immunohistochemistry and confocal microscopy. Similar levels of P2X1, P2X2, P2X3, P2X7 and P2Y2 were found in the endothelial cells in all vessels examined while the levels of P2X5 and P2X6 were uniformly lower. A clear difference was measured in P2X4 expression between arteries and veins. Both radial and internal mammary arteries exhibited very low levels of P2X4 whereas the level in the saphenous vein was 14.6 fold higher (P<0.0001), approaching that of the major receptor subtypes. These data showing strong expression of P2X4 in veins have implications for the choice of vessels used in coronary artery bypass grafts given that P2X4 is involved in calcium influx into endothelial cells, modulates blood vessel contractility and is up-regulated in situations involving intima proliferation suggesting vein grafts are more susceptible to developing atherosclerosis.