The Kidney Cortex Slice Technique as a Model for Sodium Transport In Vivo A Qualitative Evaluation

Bojesen. E. and P. P. Leyssac. The kidnty cortex slice technique as a model for sodium transport in vivo. A qualitative evaluation. A cta physiol. scand. 1965, 65 , 20–32. — Morphologically the tubules of slices incubated at 37°C present thrmselves as occluded with greatly swollen cells in contrast to the open ancl distended tubules with well‐defined and cubic cells in vivo. The cellular sodium and potassium concentrations of incubated slices differ markedly from the calculated intra‐cellular concentrations in the functioning cells, which were found to be: 4–15 μ eq Na + /g cellular Water and 123–135 μeq K + /g cellular water. Efflux studies on slices incubated with radioactive sodium did not disclose any active component when flushed with Ringer solutions of different electrolyte composition and temperatures, or in the presence of metabolic inhibitors. At a sulfate concentration of 6 mM, at which concentration the volume of distribution was equal to that of sodium, the curves on the log. of efflux rates of the two species of ions were parallel during eluation of almost the entire amount. The results suggest that at least a major fraction of sodium in cortical slices is in diffusion equilibrium with the surrounding medium. The turnover rate of sodium in the remaining minor fraction of the sodium pool subjected to active transport must be of an order of magnitude comparable to the diffilsion rate of sodium in the thin slices and thereforc faster than the turnover rate of intracellular sodium of striated muscles.