Increasing the intracellular Na+ concentration induces differentiation in a pre-B lymphocyte cell line.

The ability of lipopolysaccharide (LPS), a polyclonal B-cell mitogen, to induce differentiation in the pre-B cell tumor line 70Z/3 can be mimicked by drugs that increase the intracellular Na+ concentration. Pharmacologically increasing the cellular Na+ content with monensin, a sodium ionophore, or ouabain, a specific inhibitor of Na+, K+-ATPase, induces surface IgM expression in these cells. We have shown that LPS stimulates uptake of Na+ through an amiloride-sensitive pathway. These results show that the essential action of LPS to induce surface IgM expression is activation of a Na+ uptake system.