A rapid phytohemagglutinin induced alteration in lymphocyte potassium permeability

The exposure of rat and human lymphoid cells to mitogenic concentrations of phytohemagglutinin resulted in an apparent decrease in cellular K+ without a significant change in cellular Na+ when the cells were washed with isotonic Hepes buffered choline chloride prior to cation determination. The apparent reduction in total cellular Na+ plus K+ concentration, however, was not accompanied by a change in cell volume. We inferred that the constant cell volume could occur only if the lost intracellular K+ was exchanged for an external cation during the washing procedure used to prepare cells for Na+ and K+ measurement. This inference was supported by the quantitative recovery of lost cellular K+ in the choline chloride washing solution and the demonstration that a comparable proportion of 86Rb+ (K+ analogue) 42K+ was lost from prelabelled cells during choline chloride washing. Use of medium 199 with Hanks salts, 150 mM NaCl, or 100 mM MgCl2 as the washing solution did not prevent K+ exchange although exchange was less in the presence of MgCl2. These findings indicate that phytohemagglutinin produces a rapid alteration in lymphocyte plasma membranes so as to allow abnormal K+ exchange. This observation is of importance because investigators who measure intracellular solutes in phytohemagglutinin-treated lymphocytes must consider the possibility of lossduring preparative washes. Also, changes in membrane permeability following phytohemagglutinin treatment may modulate mitogenesis and/or permit the transmission of chemical messages between cells.