Effects of Reactive Oxygen Species on in vitro Filtration of Water and Albumin across Glomerular Basement Membrane

Most of the interest in the glomerular basement membrane (GBM) stems from the observation that it undergoes morphological changes in renal disease. Studies on persistent proteinuria in experimental animal models have shown that the permeability properties of the GBM have been altered as a result of protein degradation and cross-linking of type IV collagen via its NC1 domains promoted by reactive oxygen species (ROS) and extrusion of tubular cell contents. We used the in vitro ultrafiltration technique to assess permeability properties of bare isolated GBM films to water and albumin in the Munich Wistar Fromter rat model of glomerular injury. Hydraulic permeability for water and albumin solutions and albumin fractional clearances were measured for rats treated with lisinopril [an angiotensin converting enzyme (ACE) inhibitor] and were compared with those measured for rats treated with dimethylthiouria (an ROS scavenger) and their control groups, at four pressure levels (50, 100, 200, and 300 mmHg). The ACE inhibitors and ROS scavengers treatment regimens for studied rats in addition to significantly lowering their systolic blood pressure and urinary protein excretion values to normal levels, have significantly increased their in vitro hydraulic and Darcy permeability, which is a measure of the intrinsic hydraulic conductance of the GBM, either in the absence or presence of albumin; in comparison with control animals. We believe that these favorable effects may derive from ROS scavenging beneficial effects that preserve the GBM protein structure by reducing entactin and laminin degradation and type IV collagen cross-linking.