Analysis of Urinary and Plasma Electrolytes in a Rat Model of Unilateral Ureteric Obstruction (UUO)

Abstract

Following unilateral ureteric obstruction (UUO)., hydronephrosis is associated with long term reductions in renal blood flow (RBF) and glomerular filtration rate (GFR)., tubular resistance to arginine-vasopressin (AVP)., and reduced expression of aquaporin water channels and sodium (Na⁺) and urea transporters. During UUO., renal function is contingent upon adaptive changes in the contralateral kidney. In the short term this response is associated with an increased GFR and a reduced expression of Na+ transporters. We aimed to assess global renal function in UUO., including a comparison between the obstructed and non-obstructed kidneys.

Adult male rats were subjected to UUO of either 3 or 10 days duration. Control rats underwent sham surgery. Before release of the ureteric ligature., blood and both bladder and obstructed renal pelvis urine was sampled., then both kidneys harvested. Urinary and plasma electrolytes and osmolality., and kidney weights., were measured.

We observed i) mild uraemia in the obstructed animals., ii) extreme dilution of urine from the pelvis of the obstructed kidney in the absence of noteworthy alterations in plasma ions., and iii) evidence indicative of a contralateral diuresis/natriuresis.

To the best of our knowledge., this is the first study simultaneously examining such an extensive range of urinary (bladder and obstructed renal pelvis) and plasma markers of renal function in UUO. The results demonstrate that UUO is associated with a small deterioration in overall renal function and marked changes in renal electrolyte handling., leading to changes in the composition of urinary output from both the non-obstructed and obstructed kidneys