Advia 120 cellular hemoglobin concentration (CHC) frequency distributions in SS reticulocytes. Histograms for reticulocytes (black) are shown against the backdrop of the entire RBC population (gray) measured over time. The x-axis depicts CHC on a scale of 0-500 g/L (0-50 g/dL), and 280 and 410 g/L (28 and 41 g/dL) are represented by vertical lines. Cells were initially swollen (nystatin method) to 240 g/L (24 g/dL), then incubated in isotonic HEPES-buffered saline (HBS, pH 7.4) without (control) or with (urea) 600 mM urea. Samples were taken at various times, washed in HBS, and stored on ice until analyzed on the Advia 120. CHC distributions for cells incubated 2 hours in Cl-free media (sulfamate) without and with urea are also shown.