Differential lectin binding on walls of thoraco-cervical blood vessels and lymphatics in rats

Lectin binding in the walls of large to medium-sized blood vessels and lymphatics in the rat thoraco-cervical region was examined histochemically. The tunica intima of the aorta and superficial cervical artery showed positive reactions with wheat germ agglutinin (WGA) and Concanavalin A (ConA) but not with Dolichus biflorus agglutinin (DBA). The tunica media of the aorta exhibited intense WGA binding, especially on the smooth muscle cells, but the tunica media of the superficial cervical artery did not react with the lectin. Neither ConA nor DBA bound to the tunica media of the aorta and superficial cervical artery. The tunica adventitia of both arteries contained sites binding the three lectins, although DBA reactivity declined as the vascular diameter decreased. The tunica intima of the superior vena cava and azygos vein exhibited positive WGA and ConA binding, whereas DBA binding was noted on only part of the tunica intima of the superior vena cava and not on that of the azygos vein. The tunica media and tunica adventitia were reactive for all three lectins. The WGA and ConA binding sites in the tunica adventitia showed loose networks, suggesting lectin binding on connective tissue elements interlacing among smooth muscle bundles. Lectin binding sites in the walls of lymphatics exhibited an arrangement similar to those in the walls of the veins. Moreover valves protruding into the lumen showed intense WGA and ConA binding and scattered DBA binding. Three other lectins (Ulex europaeus agglutinin, peanut agglutinin, Maclura pomifera) were examined, but they showed no reactions with the vessels. Thus, the differential binding of lectins on the walls of blood vessels and lymphatics of various sizes suggests the functional complexity of monosaccharide residues in the vascular walls.