Mechanical membrane properties of human red blood cells and their change due to metabolic disturbance.

Blood of patients suffering from non-spherocytic chronic haemolytic anemia due to individual mutations of glucose-6-phosphate-dehydrogenase (G-6-PD) and pyruvate kinase (PK) was investigated by biochemical and rheological methods. Both enzymopathies are characterized by a strong increase (by the factor 2 to 4) in the overall RBC-rigidity and the elastic membrane shear modulus of the RBC. There was a positive correlation between the changed elastic shear modulus and the clinical picture in the case of PK deficiency and, in contrast, a negative correlation for patients with G-6-PD enzymopathies. The ability of RBC to change their shape or the static deformability is determined by the excess surface regarding to the enclosed volume, by the rheological properties of the hemoglobin content and by the membrane extension and bending moduli. The dynamic deformability is characterized by the time constant for rapid elastic and plastic deformations and becomes important for entrance and discharge processes in the microcirculation. These rheological relevant properties are subjected to metabolic control. Although for both enzymopathies the mechanism of hemolysis is not understood in detail, it has to be assumed that PK deficient RBC are mostly phagocytized and on the other hand G-6-PD deficient cells are destroyed to a higher extent by intravasal hemolysis. The aim of this study was to investigate whether or not expected changes in the RBC membrane structure due to the decreased ATP production by PK enzymopathies and diminished NADPH production by G-6-PD deficiencies result in abnormal mechanical membrane properties. The answer should give a better understanding of the premature RBC destruction.