Erythroid differentiation factor stimulates hydrolysis of polyphosphoinositide in Friend erythroleukemia cells

We examined an early action of erythroid differentiation factor (EDF), a polypeptide which induces differentiation of Friend murine erythroleukemia (MEL) cells. (Eto et al., Biochem. Biophys. Res. Commun. 142: 1095-1103, 1987). In MEL cells, EDF caused a rapid and transient increase in cytoplasmic concentration of free calcium, Ca2+]c. EDF increased Ca2+]c even in the absence of extracellular calcium. When 3H]inositol-labeled MEL cells were incubated with EDF, EDF rapidly increased radioactivity in inositol trisphosphate, bisphosphate and monophosphate. EDF also increased 3H] diacylglycerol in 3H]arachidonate-labeled MEL cells. These results indicate that EDF increases Ca2+]c by stimulating hydrolysis of polyphosphoinositide.