Effect of Partial Nephrectomy on the Clearance 01 ~ Inulin and Pah ~ N the Rat

Chronic renal disease in man, whether it be the result of chronic glomerular nephritis, chronic pyelonephritis, or vascular disease, is associated with a loss of total nephron mass (1). Patients with chronic renal disease maintain renal function only to the extent that the remaining nephrons are able to compensate for those which have disappeared. The investigation of this process of functional compensation which accompanies the reduction in renal mass is critical to an understanding of chronic renal insufficiency. There are many reports of measurements of renal function in patients with chronic renal disease; these have been made by conventional clearance methods (2-4). In general the results of these studies indicate the residual glomeruli show a greater compensatory activity in response to the decrease in nephron population than do the residual tubules which are left. In none of these studies were the functional measurements coupled with determination of the amount of renal tissue remaining at autopsy, and the only information bearing on this point is contained in a report by I-Iayman, Martin, and Miller (5), who compared creatinine clearance in patients with chronic Bright's disease with the number of glomeruli found in their kidneys at autopsy. The extent to which remaining nephrons can compensate for a reduction in their number has also been studied in animals subjected to partial nephrectomy. In partially nephrectomized dogs, which develop raised blood urea levels and polyuria if sufficient renal tissue be removed (6), glomerular filtration rate, measured either by creatinine clearance or inulin clearance, is not reduced to as great an extent as would be expected considering the amount of renal tissue removed (7-10). Findings of a similar nature were reported in the partially nephrectomized rat where the ereatinine clearance is greater than would be expected in view of the amount of loss of renal tissue (11); it should be noted, however, that creatinine clearance is an uncertain measure of glomerular filtration in the rat. None of these studies in animals so far has