Angiotensin II modulates glomerular capillary permselectivity in rat isolated perfused kidney

Studies in experimental animals and humans have documented that inhibition of the renin-angiotensin system by angiotensin-converting enzyme inhibitors reduces urinary protein excretion rate and retards the development of renal injury. Here we sought to investigate whether angiotensin II (AII) modified the size-selective properties to macromolecules of the glomerular capillary barrier in isolated perfused rat kidney preparation. Compared with basal values, continuous AII infusion into the renal artery at the rate of 3 or 8 ng/min, but not at 0.6 ng/min, induced a progressive and significant increase in urinary protein excretion rate. Evaluation at the sieving properties of the glomerular barrier by fractional clearance of polydisperse Ficoll showed that AII significantly enhanced the filtration of tracer molecules of radii ≤34Å. All-induced changes in urinary protein excretion rate and in Ficoll fractional clearance were completely prevented by pretreatment with the specific All Type 1 receptor antagonist SR 47436.