Significant calcium accumulation in fragile erythrocytes by dietary restriction in mice

Previously we reported that mice adapted to a 40% dietary restriction showed shortened erythrocyte life span (Internat. J. Vit. Nutr. Res. 1989, 59, 406-412). To clarify the mechanism of this phenomenon, influences of dietary restriction on erythrocyte fragility and on some factors associated with erythrocyte deformability were investigated. Forty percent dietary restriction caused an increase of erythrocyte osmotic fragility, a remarkable decrease of ATP levels and a striking accumulation of calcium in erythrocytes. In the diet restricted mice, it was further observed in the erythrocytes that the activity of rate limiting enzymes of glycolysis was significantly decreased. Remarkable decreases of the activities of calmodulin and membrane Ca2+/Mg2(+)-ATPase were also demonstrated in the erythrocytes from the diet restricted mice. These results strongly suggest that the fragile and short-lived erythrocytes in the diet restricted mice may be caused by the decreased activity of pumping out calcium from the cells. The fragile erythrocytes may be destroyed and removed from the blood flow earlier than flexible erythrocytes of the control mice. However, it is also suggested that the essential function of the erythrocytes, the oxygen supply to the peripheral tissues, may be maintained as 2,3-bisphosphoglyceric acid levels were not altered with erythrocyte aging in spite of the decreased glycolytic activity in the diet restricted mice.