Glomerular filtration changes during renal artery infusion of various hypertonic solutions in the dog

Summary Effects of renal artery infusion of hypertonic equiosmolar solutions of NaCl, Na₂SO₄, urea, glucose and mannitol on the glomerular filtration rate (GFR) were studied in anesthetized dogs. GFR was determined as a product of the renal plasma flow—calculated from directly measured renal blood flow and hematocrit—and the extraction ratio of exogenous creatinine (RPF·E_cr).Hypertonic solutions of urea, glucose and mannitol depressed GFR while NaCl and Na₂SO₄ were without significant effect. The change in filtration was a linear function of the inhibition of the net absolute tubular reabsorption of water (T_H2O) caused by hypertonic infusions. This relation was observed with all the infusates except Na₂SO₄ which depressed totalT_H2O but did not affect GFR. It is suggested that a definite inhibition of proximal reabsorption, probably absent with Na₂SO₄ infusion, determines the fall in GFR in osmotic diuresis.