INFLUENCE OF CALCIUM PERMEABILIZATION AND MEMBRANE-ATTACHED HEMOGLOBIN ON ERYTHROCYTE DEFORMABILITY

The present study was designed to evaluate the influence of intracellular calcium [Ca]i regulated membrane attached hemoglobin (Hb(m)) on the deformability of human RBC and ghosts. [Ca]i of RBC was elevated via the ionophore A23187 (10 muM); the deformability of RBC and resealed ghosts was determined via measuring RBC and ghost transit times through 5 mum diameter pores with the Cell Transit Analyzer (CTA). Salient results included: (1) significantly increased RBC levels of Hb(m) following ionophore treatment; (2) elevated Hb(m) with increasing lysing medium calcium concentration (0-5 mM); (3) decreased deformability of both intact RBC and ghosts with increasing Hb(m) and significant (P < 0.02 or better) linear relationships between Hb(m) and RBC or ghost transit times; and (4) an increased sensitivity to ionophore treatment/membrane attached hemoglobin for the higher percentiles of the CTA transit time distribution (i.e., tor more rigid subpopulations). Our results thus indicate that calcium-induced interaction of hemoglobin with the RBC membrane produces cellular rheological changes; in addition, they demonstrate the usefulness of the CTA system in measuring both average RBC rheologic behavior and the distribution of cellular rheologic properties within an erythrocyte population.