NMR visibility of ³⁹K and ³⁵Cl in erythrocytes and kidney tubules

The NMR visibility of 39K and 35Cl has been investigated in erythrocytes and in dog renal tubules. In erythrocytes, the 39K NMR visibility was determined by comparing the signal intensities before and after hemolysis with water and by comparing the NMR and flame photometry results. Both procedures showed a NMR visibility of 100% for intracellular potassium. The visibility of intracellular chloride in erythrocytes was estimated at 40% by monitoring the intensity of the 35Cl signal as a function of the hematocrit value. In the case of kidney proximal tubules, the 39K visibility appeared to be very low but could not be accurately determined due to the low sensitivity of the nucleus. The 35Cl signals for intracellular chloride in renal tubules were too broad to be detected.