Glomerular albumin leakage and morphology after neutralization of polyanions. I. Albumin clearance and sieving coefficient in the isolated perfused rat kidney.

In order to decide whether foot process abnormalities in nephrotic states are the cause or the consequence of proteinuria, the polycation protamine has been applied to isolated perfused rat kidneys and functional parameters and morphology have been compared. With 110 micrograms/ml protamine the albumin clearance ratio increased from 2.0 +/- 0.7 x 10(-3) in controls to 14.8 +/- 6.9 x 10(-3) 10-20 min after application and even to 98.0 +/- 30.8 x 10(-3) after 50-80 min. Micropuncture samples collected from early proximal tubules with pressure control were used to calculate the sieving coefficient which correlated with albumin clearance ratios (controls: 1.8 +/- 1.0 x 10(-3); after 10-20 min: 11.8 +/- 6.4 x 10(-3); after 50-80 min: 52.0 +/- 8.5 x 10(-3). Glomerular filtration rate decreased in the early beginning from 1.1 +/- 0.2 ml x min-1 x g-1 kidney to 0.7 +/- 0.2 ml x min-1 x g-1 kidney, but remained constant throughout the whole experiment. Despite the markedly increased albuminuria there were no changes in glomerular foot process morphology with the protamine dose used.