Acute compensatory adaptation of renal function following contralateral kidney exclusion in Brattleboro rats with diabetes insipidus.

Abstract

The function of the remaining kidney following ligation of a single renal pedicle in anesthetized rats with hereditary hypothalamic diabetes insipidus (DI) was studied using clearance methods. Values were compared with those obtained in DI rats which were sham operated. A small increase in the glomerular filtration rate of the remaining kidney was observed, which was statistically significant after 150 min. Increases in effective renal plasma flow were also observed, but these were not statistically significant. The fractional excretion rates of Na and K increased immediately after contralateral kidney ligation; as a result total Na and K excretion rates remained similar to values in sham operated animals with both kidneys intact. Fractional urine flow (V/GFR) increased by approximately 40% after contralateral ligation. Since it is unlikely that water reabsorption in the diluting segments of the nephron reduced, the increase in V/GFR was an indication that fractional fluid reabsorption in the proximal nephron was inhibited. Clearance determinations showed that the fractional reabsorption of Na in the proximal nephron was similarly reduced after contralateral ligation. Na reabsorption in the distal nephron increased, though not by enough to prevent a doubling of fractional Na excretion. The osmolalities of interstitial fluids obtained from the medulla and papilla of the contralateral kidney 2 h after unilateral renal pedicle ligation were slightly, but significantly, higher than corresponding values in sham operated rats. Salt reabsorption in the ascending limb of Henle might be enhanced immediately after contralateral renal exclusion.