Insulin-like activity of photochemically obtained monovalent monomeric concanavalin A in the presence of anti-concanavalin A antibodies: dependence on multivalency for stimulation of glucose oxidation of rat fat cells

Insulin-like action of monovalent monomeric concanavalin A (m-Con A) was examined in rat adipocytes in the presence of anti-m-Con A antiserum. The antisera from rabbits injected with m-Con A reacted with not only monovalent monomeric but also tetravalent tetrameric concanavalin A (alpha-Con A) in Ouchterlony double diffusion analysis. m-Con A alone did not show any appreciable effect on glucose oxidation of adipocytes while it slightly inhibited glycerol release stimulated by epinephrine. In contrast, exposure of adipocytes to m-Con A in the presence of antibodies to m-Con A resulted in stimulation of glucose oxidation and inhibition of epinephrine-stimulated lipolysis. The stimulation and the inhibition with m-Con A in the presence of the antibodies were of the same degree as those with alpha-Con A. Both alpha- and m-Con A were slightly active in inhibiting 125I-labeled insulin binding. These results demonstrate that the ability of anti-m-Con A antiserum to aggregate m-Con A bound to receptors on the isolated-adipocyte plasma membrane allowed m-Con A to mimic the biological activity of insulin and that the aggregation of receptors for ligands other than insulin can induce insulin-like action in rat fat cells.