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Protective effects of some neutral amino acids against hypotonic hemolysis
Y Morimoto1, K Tanaka, Y Iwakiri
1Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kobe-Gakuin University, Japan.
Abstract:
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.
Insights
Neutral amino acids affect red blood cell membrane fragility. They protect against hypotonic hemolysis at acidic pH but increase it at alkaline pH, influencing osmotic fragility through membrane shape changes.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biophysics
Background:
- Erythrocyte membranes exhibit pH-dependent osmotic fragility.
- Understanding how substances interact with cell membranes under osmotic stress is crucial.
Purpose of the Study:
- To investigate the protective effects of neutral amino acids on hypotonic hemolysis.
- To determine the influence of pH and amino acid concentration on erythrocyte membrane stability.
Main Methods:
- Induction of 50% hemolysis at varying milliosmolar (mOsM) concentrations across different pH levels (5.0, 7.0, 8.0).
- Assessment of amino acid effects (glycine, phenylalanine) on hemolysis rates and kinetics.
- Morphological observation of erythrocyte shape changes.
Main Results:
- Erythrocyte membranes showed increased fragility with decreasing pH.
- Amino acids reduced hemolysis at pH 5.0 but enhanced it at pH 8.0.
- Glycine and low-concentration phenylalanine decreased osmotic shock; high-concentration phenylalanine induced rapid hemolysis.
Conclusions:
- Neutral amino acids modulate erythrocyte osmotic fragility, with effects dependent on pH.
- Amino acid-induced membrane shape changes, such as exvagination, initially decrease fragility but can lead to membrane damage.
- Phenylalanine's interaction with membranes resembles that of amphipathic drugs.