Factors determining the plasma-membrane potential of lymphocytes

Abstract

Lymphocytes from pig mesenteric lymph node have low permeability to K+ (Rb+), Na+ and Cl-. None of these ions is in Nernst equilibrium with the plasma-membrane potential (.DELTA..psi.p). .DELTA..psi.p can be calculated from the transmembrane distribution of the permeant cation methyltriphenylphosphonium (TPMP+) in the presence of the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), which abolishes uptake into intracellular mitochondria. In normal culture medium .DELTA..psi.p was 56 mV. A similar potential was found in T-enriched pig cells and in mouse thymocytes. The contribution of electrogenic (Na+ + K+)ATPase to .DELTA..psi.p was .apprx. 7 mV. The remainder of the lymphocyte .DELTA..psi.p was a polyionic potential set up by K+ and Cl-, with a permeability coefficient for Cl- of similar magnitude to that for K+.