Ability of monovalent cations to replace potassium during stimulation of lymphoid cells

Abstract

Stimulation of hamster thymocytes, splenocytes, or lymph node cells occurred to a minimal extent in the absence of K +. This observation was found for stimulation by T-cell mitogens (phytohemagglutinin and concanavalin A), A B-cell mitogen (lipopolysaccharide), or antigen (KLH). Marginal restoration of the responses to these stimulants occurred in the presence of 0.1 m M K + and responsiveness returned to near maximal levels on addition of 1 m M K + to the cultures. Attempts to restore the responsiveness with other monovalent cations revealed an order of effectiveness of K + ≥ Rb + ⪢ NH 4 + ≥ Li +. At the 1 m M level K + and Rb + were equally effective in supporting stimulation by phytohemagglutinin while all concentrations of Li + tested (0.1–10 m M) would not support stimulation. However, addition of Li + to cultures reconstituted with 1 m M K + or Rb + revealed that this ion could enhance the phytohemagglutinin response by approximately 100% in the presence of K + and only 30% in the presence of Rb +. These data support the hypotheses that the Na,K ATPase must be active for lymphocyte stimulation to occur and that some of the biological effects of Li + on lymphocyte stimulation are mediated at the level of the Na,K ATPase.