The protective effects of some
neutral amino acids against hypotonic
hemolysis were examined at various pHs. At pH 5.0, 7.0 and 8.0, 50%
hemolysis was induced at 200, 160 and 140 mOsM, respectively, suggesting that erythrocyte membranes became more fragile to osmotic shock with decreasing pH. All
amino acids tested reduced the hypotonic
hemolysis at pH 5.0, but enhanced it at pH 8.0. It is therefore likely that these
amino acids controlled the osmotic fragility of the cell membranes. At pH 7.0,
glycine (Gly) reduced hypotonic
hemolysis with increasing concentration.
Phenylalanine (Phe) also reduced hypotonic
hemolysis at low concentrations, but had an incrementally opposite effect at high concentrations. It was suggested that Phe interacted with erythrocyte membranes in a similar way to amphipathic drugs. Kinetic studies demonstrated that hypotonic
hemolysis occurred immediately, according to osmotic shock, and that Gly and a low concentration of Phe decreased osmotic shock. Phe at a high concentration showed fast
hemolysis with a short lag-time. Gly also showed fast
hemolysis after the suppression of hypotonic
hemolysis. Morphological observations demonstrated that these
amino acids induced exvagination, exovesiculation and then invagination. It was suggested that with exvagination, the membrane expansion decreased the osmotic fragility, but the further shape change evoked membrane hole-formation.