Concanavalin a inhibits the basal and stimulated hormone release from pituitary cells in monolayer cultures

Many of the properties of the plasma membrane glycoproteins have been ~vestigated by using several lectins, including concanavalin A (con A). Although the precise mechanism of lectin action on the cell surface is not known, interaction of con A with plasma membrane involves the recognition of sugar residues [I]. Moreover, the binding of con A to cell surface macromolecules can be specifically reversed by the addition of a-methyl-D-mannoside or a-methyl-Dglucoside [2]. The interactions of con A with plasma membranes have been shown to cause a number of biological effects including cell agglutination [3], transformation of lymphocytes [4] and mitotic induction [5] and to affect membr~e enzyme activities such as 5’-nucleotidase [6], ATPase [7 ] and sialyltransferase [8]. Con A has also been found to modify the binding [9-l l] or the activity [ 12-141 of certain hormones, and to mimic several hormonal effects [15,16]. Here we demonstrate that con A is able to inhibit the basal and stimulated hormone release by rat pituitary cells in culture.