Effect of urea on volume reduction in sickle and normal reticulocytes. Cells were swollen by nystatin treatment and incubated in isotonic HBS pH 7.4 (no urea) or the same buffer plus 600 mM urea. (A-B) Sulfamate media were Cl free. Data points are means ± SEMs of 3 independent experiments. (C-D) Inhibition of DIOA. The concentration of KCC transport inhibitor, DIOA, when present, was 100 μM. Single experiments with SS and AA cells are depicted, representative of 2 others with both cell types.