Calcium response to erythropoietin in erythroleukemia cells

Erythroleukemic mouse spleen cells were analyzed by flow cytometry at three fluorescence wavelengths, two emissions for the calcium indicator indo 1 and immunofluorescence with an antiserum directed against murine leukemia retrovirus antigen. The antigen-positive subpopulation of cells responded to EPO by transiently changing indo 1 fluorescence emissions, indicating a change in cytoplasmic calcium concentration. EGTA blocked the EPO response, suggesting that Ca2+ influx may have followed EPO exposure in these cells. Antigen-negative cells showed no Ca2+ response to EPO. Infected mice all contained antigen-positive spleen cells, but, as measured by changes in indo 1 fluorescence, these subpopulations varied in their ability to respond to EPO.