Calcium Transport and Ultrastructure of Red Cells in fl - Thalassemia Intermedia

Reported findings of elevated total calcium (Ca) contents in erythrocytes (RBCs) from patients with $-thalassemia intermedia (fl-TI) prompted the question of whether the state and transport of Ca in these RBCs are similar to those in sickle cell anemia (SS) RBCs where the increased Ca is compartmentalized in endocytic inside-out vesicles and extracted by exposure of the cells to the Ca ionophore A23i 87 and a Ca chelator (ethylene glycol tetraacetic acid) and the levels of cytoplasmic free ionized Ca ([Ca2 ],) are normal. We confirmed a high total Ca content of 5i ± i 3 mol/L RBCs in splenectomized (SPX) /9-TI and 24 ± i smol/L RBCs in non-SPX fi-Tl. Unlike SS RBCs, however. most of the increased Ca was in the lighter. presumably younger /9-TI RBCs, and about half the Ca was not ionophore mobilizable but apparently firmly bound, possibly to remnants of organelles in nucleated and other young RBCs. In the denser RBCs from non-SPX /9-TI, total and extractable Ca amounts were normal. fl-TI RBCs loaded with the Ca chelator Benz 2 showed an initial influx of Ca in the