Alterations in structure, function, and Ca⁺⁺ content of thalassemic red blood cells

Dodge ghosts and their Triton extracted cytoskeletons (TS) were obtained from RBC of splenectomized (spx) and non-splenectomized (non-spx) patients with β thalassemia intermedia. No major abnormalities were seen in the polypeptide pattern of Dodge ghosts of the thalassemic patients apart from increased globin content in the spx patients (p = 0.004). The was also a large increase of globin content in the TS of both spx and non-spx patients, while the spectrin content of the TS was markedly decreased from 22 ± 2.8% in the spx patients compared to 39 ± 2% in the controls ( P = 0.006). At least part of the globin was not found at the normal band 3-binding site. The mean Ca⁺⁺ content in spx and non-spx controls was ~ 6.0 micromoles Ca/liter RBC, as compared to 26 ± 7.6 (P<0.001) in the non-spx and 85 ± 24 in the spx thalassemic patients (P<0.001). (Ca⁺⁺ + Mg⁺⁺)-ATPase activity was in the same range in RBC of patients and controls. Membrane protein phosphorylation was examined by incubation of intact cells with (³²P)Pi. There was decreased labeling of several protein bands in thalassemic RBC which are labelled in normal RBC. New phosphorylation peptides also appeared. On the other hand, there were no major differences in the phosphorylation of isolated membranes including phosphorability of spectrin. The possible etiology and consequences of the newly described RBC membrane changes in thalassemia are discussed.