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

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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.