Erythrocyte membrane alterations in thalassemia intermedia

Abstract

The erythrocyte membrane alterations were studied in nineteen beta-thalassemia intermedia patients. Solubilized erythrocyte membrane proteins were gel-filtered and high-molecular-weight aggregates were isolated and analyzed for denatured hemoglobin derivatives. All the patients presented increased amounts of membrane-bound heme, hemichromes and immunoglobulins, together with aggregation and oxidation of band 3. The basal activity of the erythrocyte pentose-monophosphate-pathway was normal, whereas a lower susceptibility to in vitro methylene blue stimulation was observed. In five randomly-selected patients, whole blood viscosity resulted approximately normal, while filterability was significantly lower, suggesting a decrease in red blood cells deformability. A relation between hemichrome-induced band 3 aggregation and rheologic modifications of red blood cells was observed. Hemichrome binding to band 3 seems likely to be an important event leading to membrane damages and, hence, responsible for erythrocytes removal from blood circulation by the phagocytic system. Density gradient separation of erythrocyte subpopulation was performed in a selected case and the same biochemical, redox status and rheologic parameters were determined. The oldest cells have no detectable hemichromes and their deformability is better than that of cells containing a relevant amount of hemichromes.