βsChain Turnover in Reticulocytes of Sickle Trait Individuals with High or Low Concentrations of Haemoglobin S

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Abstract
Reticulocytes, isolated from the blood of sickle cell trait donors with either low (25-30%) or high (40-42%) Hb S concentrations, were incubated with [3H]leucine for various times from 1.25-60 min. Samples of the total soluble fractions of the cells were denatured with urea and mercaptoethanol. The mixtures were analyzed by electrophoresis on cellulose acetate strips. The specific radioactivities (dpm/mg) of the separated .beta.S and .beta.A globin chains were determined. The .beta.S/.beta.A ratios of globin chain specific radio activities in the reticulocytes of the low Hb S donors decreased gradually from initial values higher than 1.30 to values near unity. Faster turnover of some of the soluble, newly synthesized .beta.S chains compared to the newly synthesized .beta.A chains could explain part, but not all, of the disparity in concentrations of Hbs S and A in these people. When reticulocytes from high Hb S donors were 3H-labeled for times longer than 5 min, the .beta.S/.beta.A specific radioactivity ratios remained at or near unity. This result suggested that newly synthesized .beta.S chains were not turning over selectively in these cells. Instead, there was a relative decrease in .beta.S chain synthesis proportional to the difference in blood concentrations of Hb S and Hb A. Additional calculations suggested that the more rapid turnover of newly synthesized .beta.S chains in the low Hb S reticulocytes could explain the difference in Hb S concentrations between ''high and low Hb S'' people. These results are consistent with previous reports that an .alpha.-thalassemia gene, present in low Hb S but absent in high Hb S donors, may be responsible for the selective turnover of .beta.S chains.

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