Rates of efflux and intracellular concentrations of potassium, sodium and chloride ions in isolated fat-cells from the rat

Abstract

1. The metabolism of K⁺, Na⁺ and Cl⁻ has been investigated in isolated fat-cells prepared from the epididymal adipose tissue of rats. 2. Methods are described for measuring the intracellular water space, the rates of loss of intracellular ⁴²K⁺, ²²Na⁺ and ³⁶Cl⁻ and the intracellular concentrations of K⁺, Na⁺ and Cl⁻ in isolated fat-cells. 3. The intracellular water space, measured as the [³H]water space minus the [carboxylic acid−¹⁴C]inulin space, was 3·93±0·38μl./100mg. cell dry wt. 4. The first-order rate constants for radioisotope effluxes from isolated fat-cells were 0·029min.⁻¹ for ⁴²K⁺, 0·245min.⁻¹ for ²²Na⁺ and 0·158min.⁻¹ for ³⁶Cl⁻. 5. The intracellular concentrations of K⁺, Na⁺ and Cl⁻ were 146m-equiv./l., 18·6±2·9m-equiv./l. and 43±2·4m-equiv./l. respectively. 6. The total intracellular K⁺ content of isolated fat-cells was determined by atomic-absorption spectrophotometry to confirm the value obtained from the radioisotope-efflux data. 7. The ion effluxes from isolated fat-cells were: K⁺, 1·5pmoles/cm.²/sec., Na⁺, 1·6pmoles/cm.²/sec., and Cl⁻, 2·4pmoles/cm.²/sec. 8. The membrane potential of isolated fat-cells calculated from the Cl⁻ distribution ratio was −28·7mv.