Role of Interleukin-3 in the Regulation of Intercellular K + Homeostasis in Cultured Murine Hematopoietic Cells

Comparative fluorimetric, flow cytofluorimetric and fluorescence ratiometric determinations of intracellular K + concentrations in murine haemopoietic cells (FDCP-Mix clone A4) cultured in the presence and absence of the specific growth factor Interleukin-3 were carried out with the fluorescent potassium-binding benzofuran-isophthalate acetoxymethyl ester probe. Cell suspensions kept in the absence of Interleukin-3 for 5 hours exhibited lower fluorescence intensities and smaller fluorescence ratios than their growth-factor-replete counterparts, an effect found to be reversible by readdition of the growth factor. It is concluded that Interleukin-3 deprivation of-these cells leads to loss of intracellular K +. It is tentatively suggested that this deprivation-induced K + loss might be associated with an early event in apoptotic cell death.