Quantitative excretion of water and sodium load by isolated dog kidney: autonomous renal response to blood dilution factors.

Totally isolated dog kidneys of the same pairs are perfused with heparinized blood under identical conditions, one of the kidneys being submitted to a supplementary isotonic or hypotonic saline load. Excess sodium is excreted quantitatively as well as excess solute-free water. Autonomous renal response depends on blood dilution, changes in blood pressure being excluded as well as influence of volume expansion or of extrarenal hormonal factors. The experiments demonstrate kidney ability to control quantitatively fast changes in saline balance by autonomous mechanisms in the sense of intrarenal feed-back type relation to blood composition. Dilution factors (plasma sodium, potassium, proteins) control excretion primarily by adjustment of tubular reabsorption to filtration. Moreover, the absence of relation between basal control excretion and response to saline loading in the present experiments suggest that different mechanisms could insure long duration adjustment of the kidney to a definite blood composition and saline balance. It is demonstrated that many effects attributed to volume expansion can be caused by blood dilution; moreover, interference between dilution effects and specific hormonal control by eventual natriuretic factor should be avoided. © 1968 Springer-Verlag.