TRANSMEMBRANE ELECTRICAL AND PH GRADIENTS ACROSS HUMAN-ERYTHROCYTES AND HUMAN PERIPHERAL LYMPHOCYTES

Transmembrane electrical and pH gradients were measured across human erythrocytes and peripheral blood lymphocytes using equilibrium distributions of radioactively labeled lipophilic ions, weak acids and weak bases, respectively. The distributions of methylamine, trimethylamine, acetic acid and trimethylacetic acid give calculated transmembrane pH gradients (pHe-pHi) for erythrocytes of between 0.14-0.21 for extracellular pH values of 7.28-7.16. The distributions of trimethylacetic acid, DMO and trimethylamine were determined for lymphocytes, establishing upper and lower limits of the calculated pH gradient over the external pH range of 6.7-7.7. Tritiated triphenylmethyl phosphonium ion (TPMP) and 14C-thiocyanate ion (SCN) equilibrium distributions were measured to calculate transmembrane electrical potentials, using tetraphenylboron as a catalyst to facilitate TPMP equilibrium. Transmembrane potentials of -7 to -10 mV were calculated from SCN and TPMP, respectively, for red cells, and -35 to -52 mV, respectively, in the case of lymphocytes. Distributions of TPMP and K ions were determined in the presence of valinomycin over a wide range of extracellular K concentrations for red cells and the calculated Nernst potentials for TPMP compared to the calculated potential using the Goldman equation for Cl and K ions. Distributions fo TPMP, SCN and K ions were also determined for lymphocyte suspensions as a function of extracellular K and the calculated Nernst potentials for TPMP and SCN compared to the calculated K diffusion potential.