[The effect of wheat germ agglutinin on anion transport in the erythrocyte membranes].

The wheat germ agglutinin (WGA) has been recognized as the lectin that can agglutinate human erythrocytes. It is reported recently that the binding of WGA to the glycophorin blocks the morphological conversions of discocyte<-->echinocyte. Glycophorin is thought to be associated with Band 3, the anion transport protein, via the cytoskeleton proteins Band 4.1, spectrin and ankyrin. The effect of WGA on the anion transport across the erythrocyte membranes was measured by NO2- transport and NH4 Cl isotonic swelling, two different methods developed by our laboratory in recent years. The results showed that the rate of anion transport was decreased, depending on WGA concentration. This effect became saturated when WGA concentration reached 2-3 micrograms/ml. We have also observed that in certain conditions when the morphological conversion of discocyte-->elliptocyte was induced by high concentration of WGA, the rate of anion transport could be reversely increased. Furthermore, the effect of WGA on erythrocyte osmotic fragility was studied. The results indicated that the osmotic fragility was reduced after adding WGA to the erythrocyte suspension, which means the erythrocyte cytoskeleton is more stable under this condition. All effects that WGA exerted above were instantly abolished by adding N-acetylglucosamine which has specific binding sites on WGA. In conclusion, the binding of WGA to the sialic acid groups of glycophorin can lead to the conformational changes in saccharides and such changes will be transferred via glycophorin, cytoskeleton to Band 3, which causes the final change of anion transport. The effect is indirect, so the change is small (approximately 10%).(ABSTRACT TRUNCATED AT 250 WORDS)