Relative roles of glomerular filtration and tubular reabsorption in denervation diuresis

Abstract

Experiments have been carried out on anesthetized, laparotomized dogs in which urine samples were collected from both kidneys after acute denervation of one. Renal functions were estimated by standard procedures with creatinine clearance (C_Cr) as an index of glomerular filtration rate. Urine flow and solute excretion were greater from the denervated kidney (D) than from the innervated kidney (I) under all conditions of solute diuresis. The magnitude of denervation diuresis, D/I for urine flow, was directly related to the relative excess of electrolyte excretion on the denervated side, D/I for electrolyte excretion rate. D/I for electrolyte excretion was not correlated with D/I for C_Cr and remained above 100% in all experiments despite a fall of D/I for C_Cr below 100% in 10 of 30 comparisons. Since excessive electrolyte excretion by the denervated kidney could not be explained by greater total filtration rate, it was reaffirmed that denervation caused a defect in proximal tubular reabsorption of sodium, either by decreased reabsorptive activity of all tubules or by redistribution of filtration toward tubules of lesser reabsorptive capacity.