Studies of Experimental Renal Failure in Dogs. I. Effect of 5/6 Nephrectomy on Concentrating and Diluting Capacity of Residual Nephrons*

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Abstract
The effect of increased osmotic load on concentrating and diluting abilities was studied in dogs before and after resection of 5/6 of the renal mass. During maximal antidiuresis and sustained water diuresis graded infusions of urea were given to normal and 5/6 nephrectomized dogs in order to compare these functions at the same solute load per functioning mass (as indicated by glomerular filtration rate). There was impairment of both maximal and minimal urine/plasma (U/P) osmolal ratios at basal and at increased solute excretion rates in the kidney remnant animals. When solute load was expressed per nctioning renal mass in the 2 groups, the subtotally nephrectomized dogs had normal maximal U/P osmolal ratios and enhanced minimal U/P osmolal ratios compared with normal. The adjusted rates of free water clearance (CH2O/GFR) and of free water reabsorption (TcH2O/GFR) were increased and equal to normal, respectively, after 5/6 nephrectomy. These findings differ from observations in patients with functional mass reduced by diffuse parenchymal disease; thus, factors other than increased solute load per residual nephron may contribute to the altered concentrating and diluting ability seen in chronic renal disease.