Ionic fluxes in the rat portal vein and the applicability of the Goldman equation in predicting the membrane potential from flux data.

Abstract

AbstractWahlstrom, B. A. Ionic fluxes in the rat portal vein and the applicability of the Goldman equation in predicting the membrane potential from flux data. Acta physiol. scand. 1973. 89. 436–448.The sodium, potassium and chloride effluxes from the rat portal vein were measured using radioactive tracer ions. It was found that the sodium efflux attributable to an intracellular compartment was very slow, with a rate constant of 4.66×10‐4 s‐1, and the corresponding intracellular sodium only 3.0 mmol/kg wetweight. The intracellular potassium exchanged with a rate constant of 2.15×10‐4 s‐1 and contained 45.5 mmol/kg wetweight. The intracellular chloride content was 14.7 mmol/kg wetweight, exchanging with a rate constant of 10.55 × 10‐4 s‐1. From these data the permeabilities of Na, K and CI were calculated to 0.130, 3.81 and 3.11 ×10‐8 cms‐1 respectively. The relative permeabilities PK: PNa: PC1 were 1: 0.034: 0.816, and from these values the Goldman equation predicted a membrane potential of ‐42.3 mV. The actual membrane potential, measured by glass microelectrodes, was ‐ 45 mV. It was concluded that the membrane potential in the rat portal vein in normal solution can be predicted from the permeabilities and distribution of K and CI, while Na plays an insignificant part.