[Natriuretic reaction of the vertebrate kidney].

After injection of a 10% solution of NaCl, the kidney of rats, and to a lower extent that of hens, rapidly excretes the excess sodium. Effective sodium excretion in homoiothermic animals is based on high level of glomerular filtration and proximal reabsorption. After injection of a 10% solution of NaCl to the Lamprey Lampetr fluviatilis and frog Rana temporaria, sodiumuretic reaction of the kidney was less evident. During water diuresis, cells of renal tubuli of lampreys, frogs, hens and rats produce high concentration gradient between the blood serum and urine, preventing loss of sodium. In evolution, the kidney was formed presumably as an organ which prevents sodium loss from the organism; this function remains highly effective in all vertebrates, whereas in homoiothermic animals the kidney attains also the capacity for rapid extrusion of excessive sodium.