LECTIN-INDUCED INCREASE IN MICROVASCULAR PERMEABILITY TO COLLOIDAL CARBON IN-VITRO MAY INVOLVE PROTEIN-KINASE-C ACTIVATION

Two plant lectins, wheat germ agglutinin (WGA) and concanavalin A (Con A), which are known to bind to endothelial cells (ECs) were found to increase the leakage of colloidal carbon (CC) into the walls of microv essels in the villi of rat small intestine, when added to a gelatin-co ntaining perfusate (GPSS) at a concentration of 10 mu g/ml. Pretreatme nt of the microvessels with the protein kinase C (PKC) inhibitor Ro 31 -8220 (1x10(-6) M) significantly reduced this effect. In contrast, the leakage of CC in response to A23187 (1 x 10(-4) M) was not affected b y Ro 31-8220. Peanut agglutinin (PNA) and succinyl concanavalin A (Suc cCon A), which do not bind to ECs, had no effect at a concentration of 10 mu g/ml. A lower concentration of WGA (1 mu g/ml) had no significa nt effect of its own, but significantly reduced the leakage of CC in r esponse to both platelet-activating factor (PAF, 5 x 10(-6) M) and 5-h ydroxytryptamine (5-HT, 1 x 10(-4) M), but not to beta-phorbol 12,13-d ibutyrate (PDB, 1 x 10(-6) M). These results suggest that all these ef fects of WGA and Con A involve cell surface receptors, albeit in a non specific way. A possible mode of action is discussed.