Glomerular hyperpermeability after acute unilateral ureteral obstruction: Effects of Tempol, NOS, RhoA, and Rac-1 inhibition

It is well known that proteinuria following urinary tract obstruction is mainly of a tubular nature. However, it is unknown whether there are also changes in glomerular permeability. In this study, we compared glomerular sieving coefficients (θ) of polydisperse fluorescein isothiocyanate (FITC)-Ficoll 70/400 following a 120-or 180-min unilateral ureteral obstruction (UUO) in anesthetized Sprague-Dawley rats. Samples were collected from the obstructed kidney at 5, 15, and 30 min postrelease and analyzed by means of high-pressure size-exclusion chromatography. After 120-min UUO, mean θ for Ficoll_70Å was increased (P < 0.01) from 2.2 ± 0.5 × 10⁻⁵ (baseline) to 10.6 ± 10 × 10⁻⁵ 15 min postrelease (highest value). After 180-min UUO, mean θ for Ficoll_70Å was further increased (P < 0.001) from 1.4 ± 0.5 × 10⁻⁵ (baseline) to 40 ± 10 × 10⁻⁵ at 5 min postrelease (highest value). Administration of a reactive oxygen species (ROS) scavenger (Tempol; 1 mg·kg⁻¹·min⁻¹) partly abrogated the permeability effects following 120-min UUO but not after 180 min. Moreover, administration of the RhoA kinase inhibitor Y-27632, the nitric oxide synthase inhibitor N^G-nitro-_L-arginine methyl ester, or Rac-1 inhibition did not ameliorate glomerular hyperpermeability following 180-min UUO. We show, for the first time, that acute UUO results in marked elevations in glomerular permeability. In addition, our data suggest a time-dependent pathophysiology of UUO-induced hyperpermeability, where reactive oxygen species generation may play an important role in the early stages.