Role of extracellular Na and K in lymphocyte activation

Abstract

The transmembrane electrical potential has been measured across human peripheral blood lymphocytes under culture conditions using equilibrium distributions of the lipophilic cation ³H‐tetraphenylphosphonium (TPP). The TPP equilibrates to a steady‐state level that gives calculated voltages of −80 mV for unstirnulated lymphocytes. This value of Ihe potential is constant during the first few hours of succinyl concanavalin A stimulation. When the transmembrane electrical potential is lowered by isotonic replacement of Na with K, this neither by itself stimulates proliferation nor does it inhibit mitogen‐stimulated proliferation. Lymphocytes with similar membrane potentials, such as those incubated in normal‐Na MEM and low‐Na‐mannitol MEM, exhibit drastically different pro‐liferative responses to mitogen stimulation (Deutsch et al., 1981). These results show that isotonic replacement of K for Na prevents low Na inhibition of DNA synthesis and that at least during the first 2.5 hours of lymphocyte activation transmembrane electrical potential per se does not play a significant role in the activation process.