PROTECTIVE EFFECTS OF SOME NEUTRAL AMINO-ACIDS AGAINST HYPOTONIC HEMOLYSIS

The protective effects of some neutral amino acids against hypotonic h emolysis were examined at various pHs. At pH 5.0, 7.0 and 8.0, 50% hem olysis was induced at 200, 160 and 140 mOsM, respectively, suggesting that erythrocyte membranes became more fragile to osmotic shock with d ecreasing pH. All amino acids tested reduced the hypotonic hemolysis a t 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. A t pH 7.0, glycine (Gly) reduced hypotonic hemolysis with increasing co ncentration. Phenylalanine (Phe) also reduced hypotonic hemolysis at l ow concentrations, but had an incrementally opposite effect at high co ncentrations. It,vas suggested that Phe interacted with erythrocyte me mbranes in a similar way to amphipathic drugs. Kinetic studies demonst rated that hypotonic hemolysis occurred immediately, according to osmo tic shock, and that Gly and a low concentration of Phe decreased osmot ic shock. Phe at a high concentration showed fast hemolysis with a sho rt lag-time. Gly also shelved fast hemolysis after the suppression of hypotonic hemolysis. Morphological observations demonstrated that thes e amino acids induced exvagination, exovesiculation and then invaginat ion. It was suggested that with exvagination, the membrane expansion d ecreased the osmotic fragility, but the further shape change evoked me mbrane hole-formation.