Excretion and tubular reabsorption of sodium,glucose and phosphate by isolated dog kidneys. Influence of blood dilution

Summary Sodium, glucose and phosphate reabsorption and excretion have been investigated in totally isolated dog kidneys. The potentiation by furosemide of the natriuresis caused by saline loading of the preparation is quantitatively comparable to that observed in the whole animal; the decrease of proximal reabsorption together with its partial distal compensation correspond primarily to a direct renal effect of blood dilution. Glucose reabsorption is proportional to glomerular filtration rate; it does not differ from the values found in the whole dog. Phosphate reabsorption is proportional to the filtered phosphate load up to a value of the latter of 10 mg P/min/100 g; at higher values a true TmPO₄ is reached which is higher than in normal or thyroparathyroidectomized dogs. Blood dilution exhibits no influence on TmG. The influence of blood dilution on fractional P reabsorption depends on the P filtered load. At low values of this load, P reabsorption is not influenced; at high values, reabsorption is significantly reduced by dilution. No relationship is demonstrated between glucose and sodium reabsorption inasmuch as the latter is under direct dependence on blood dilution. Furosemide (10^–4 M) induces no significant change in either TmG, P reabsorption or glomerular filtration rate.