Reduced sodium pump activity in inositol-deficient HL-60 cells: no evidence of control by protein kinase C

HL-60 cells were cultured in normal and inositol-deficient media. The inositol-deficient cells showed reduced sodium pump activity, as measured by ouabain-sensitive 86Rb+ uptake. The protein kinase C inhibitors staurosporine and H7 did not affect uptake in either normal or inositol-deficient cells. However, U73122, a steroidal inhibitor of phosphoinositidase C, inhibited uptake in both types of cells. Activators of protein kinase C had no effect on Rb+ entry. The inositol deficiency is not considered to affect the sodium pump by a mechanism involving diacylglycerol and protein kinase C.