Increased resistance of immature red cells of rat and dog to osmotic lysis

Mature male rats were injected with radioiron, which labeled immature red cells that were in the stage of hemoglobin synthesis at the time. Washed cells were subjected to lysis by hypotonic saline at 14 intervals ranging from 1 to 85 hours after ⁵⁹Fe injection. Lysis curves were determined colorimetrically (for the whole population) and by scintillation counting of ⁵⁹Fe gamma rays (for the labeled population). Newly labeled rat red cells are much more resistant than mature erythrocytes. The mature curve of osmotic resistance is acquired about 67 hours after injection. The delivery of labeled cells continues for more than 36 hours, so the maturation of osmotic properties of a typical rat red cell takes about 30 hours from entry into the circulation. Washed dog cells behave in similar fashion but delivery continues for three days and the mature lysis curve does not appear until five days after labeling, so that maturation takes about two days. Preincubation of cells is requisite for the appearance of osmotic resistance, but the basis of the incubation effect is not yet known.