Elevated tubular proteinuria, albuminuria and decreased urinary N-acetyl-β-D-glucosaminidase activity following unilateral total ureteral obstruction in rats

Abstract

Urinary tubular proteinuria and N-acetyl-β-d-glucosaminidase (NAG) activity has not yet been studied after unilateral total ureteral obstruction (UTO). The aim of the study was (1) to evaluate in a longitudinal study (7 weeks) the behaviour and the potential clinical value of tubular proteinuria and urinary NAG activity after UTO; (2) to study the physiopathology of the non-obstructed contralateral kidney by using these two different markers of tubular damage. Methods: in 28 female, adult Wistar rats (UTO: n= 16, sham: n= 12), tubular proteinuria and urinary NAG activity were measured before and 1 and 5 weeks after surgery. Results: a significant (P < 0.01) increase in tubular proteinuria/creatinine ratio and urinary creatinine and a decrease in urinary NAG activity was found 1 week after UTO. All parameters normalized after 6 weeks. Albuminuria increased progressively (P < 0.01) during the study. Conclusion: tubular proteinuria increases during the first week following UTO in rats. The initial increase of low molecular weight proteins following UTO is not due to tubular damage as no parallel increase of urinary NAG was found. We suggest an initial tubular overperfusion with primary urine, due to an increased single nephron glomerular filtration and overruling the reabsorption capacity of the proximal tubules.