SITE OF DECREASED FLUID REABSORPTION AFTER RELEASE OF URETERAL OBSTRUCTION IN RAT

  • 1 January 1976
    • journal article
    • research article
    • Vol. 87  (3) , 397-410
Abstract
Fluid reabsorption in surface nephrons was studied by micropuncture 3 h after release of complete left ureteral ligation (LUL) or after unilateral release of bilateral ureteral ligation (BUL). In 11 rats with LUL, glomerular filtration rate(GFR) averaged 0.23 .+-. 0.04 ml/min in the experimental vs. 1.25 .+-. 0.11 ml/min in the control kidney. GFR averaged 0.18 .+-. 0.02 ml/min in BUL. Single nephron glomerular filtration rate (SNGFR) was decreased in the experimental kidney of LUL or BUL when determined at proximal or distal sites as compared to the SNGFR determined in shams or the left kidney following right ureteral ligation (RUL). Fractional water excretion was increased after release of obstruction. LUL 2.72 .+-. 0.66%; BUL 12.3 .+-. 2.82% when compared to sham-operated rats (0.48 .+-. 0.07%) or to the untouched kidneys of the RUL group (0.60 .+-. 0.09%). Despite increased water and Na excretion after release of unilateral ureteral ligation and BUL there were marked differences in tubular fluid reabsorption between these 2 groups. Following release of LUL there was increased fractional water reabsorption along the accessible length of surface nephrons of the experimental kidney. At 55% of proximal tubular length tubular fluid to plasma inulin ratios (TF/Pin) averaged 4.02 .+-. 0.02 in LUL vs. 2.18 .+-. 0.06 in shams. The mean TF/Pin at 90% of distal tubular length was 31.0 .+-. 1.37 in LUL vs. 10.6 .+-. 0.08 in sham-operated rats. Water reabsorption after BUL was slightly but significantly suppressed proximally (TF/Pin 1.95 .+-. 0.02) and markedly depressed distally (TF/Pin 3.35 .+-. 0.29). The change in fluid reabsorption observed after relief of LUL is apparently located at a site beyond the accessible length of surface nephrons, most likely in the collecting duct. The data could also be explained by alterations in fluid reabsorption in deep nephrons. The changes in fluid reabsorption seen following release of BUL reflect the additive effects of release of obstruction and a marked reduction in functioning nephron mass.

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