Changes in glomerular filtration rate during complete ureteral obstruction in rats

Abstract

The effects of complete ureteral obstruction on glomerular filtration rate (GFR) remain to be clearly delineated. Existing data indicate that the process of glomerular filtration continues for at least several hours following the onset of obstruction [1–3]. In place of standard clearance techniques, which depend on continuous urine flow and hence are not applicable to the obstructed kidney, other methods of estimating GFR during urinary tract obstruction have been devised. By use of a modification of the stop-flow technique [4] in dogs [3] and rats [2], by measurement of the arteriovenous inulin difference across the kidney in rats [1], and by determination of the disappearance rate of inulin from the blood following a single inulin injection in rats [1], previous investigators have provided evidence that filtration continues during ureteral obstruction. These methods, however, were capable of yielding only rough estimates of GFR. Moreover, in two of these studies, the data were all obtained during mannitol or hypertonic saline loading, within the first few minutes of obstruction [2, 3|. The third study [1] presented results for up to 6 hours following the onset of obstruction, but the data sufficed only to demonstrate the occurrence of filtration, without permitting calculation of GFR. Thus, none of these studies has clearly defined the time course of GFR following onset of obstruction.