Excretion of sodium and water by kidneys in situ and by transplanted kidneys following isotonic, hypotonic, iso-oncotic and hyperoncotic intravenous infusions in sodium-loaded and sodium-deprived dogs.

The excretion of sodium and water following isotonic, hypotonic, iso-oncotic and hyperoncotic intravenous infusions has been investigated in the kidneys in situ and in transplanted kidneys of narcotized dogs previously submitted to sodium-enriched or-deprived diets. The fractional excretion of sodium depended basically on the cumulative effect on the kidney of the changes in plasma oncotic pressure, plasma sodium concentration, and haematocrit. The differences in excretory responses of sodium-loaded or-deprived animals did not depend on differences in the distribution of infused fluids between intra- and extravascular compartments, but to the sensitivity of the kidney itself to the direct cumulative effect of these non-specific changes in blood composition.