The effects of the lectins, wheat germ agglutinin (WGA) and concanavalin A (Con A) on endothelium intact pre-contracted rabbit aorta were investigated. WGA (8.3 microM) produced endothelium-dependent relaxations, while Con A (4.3 microM) produced a partially endothelium-dependent relaxation. The endothelium-dependent relaxations to WGA were completely reversed by N-acetylglucosamine, haemoglobin and methylene blue and were partially reversed by NG-monomethyl-L-arginine (L-NMMA). It is suggested that WGA works as an agonist in releasing endothelium-derived relaxing factor (EDRF) from the endothelium of rabbit aorta by interacting with a glycosylated receptor on endothelial cells.