Na/Mg exchanger activity in normal and sickle erythrocytes. (A) The activity of the exchanger was measured in Mg²⁺-loaded cells (total cellular [Mg²⁺] = 13.5 ± 0.39 mmol/L cells) as described in “Patients, materials, and methods.” The error bars represent the mean ± SE of more than 30 experiments carried out in triplicate. ^*P < .0001. (B) Na/Mg exchanger activity in density-separated normal and sickle erythrocytes. The MCHC and reticulocyte content was measured using an aliquot of each cell fraction in an ADVIA 120 automatic hemo-analyzer (Bayer, NY). The activity of the exchanger was measured as described in “Patients, materials, and methods” and corrected by MCV of each independent fraction. Fraction reticulocyte (%): Hb AA (28.8 g/dL = 3.3 ± 0.2, 31.4 g/dL = 1.7 ± 0.1, 33.1 g/dL = 0.5 ± 0.05); Hb SS (27.1 g/dL = 13.8 ± 0.9, 31.1 g/dL = 7.6 ± 0.3, 34.0 g/dL = 3.1 ± 0.9). Values are the mean ± SE of 2 experiments in triplicate determinations.