Albumin interaction with the glomerular capillary wall in vitro.

The binding of albumin to the glomerular capillary wall was studied using albumin-gold in perfused kidneys, the interaction of [3H]albumin with isolated glomeruli at 37 degrees C and 4 degrees C and the interaction at [3H]albumin with purified basement membrane. The albumin-gold was found to bind predominantly to the basement membrane and this interaction could be dissociated with high concentrations of albumin. There was binding of albumin to isolated rat glomeruli which exhibited temperature dependence. Glomeruli exhibited a binding site at both 37 degrees C and 4 degrees C with an association constant in the range of 1 to 3 x 10(4) M-1 that bound 7 x 10(13) molecules/glomerulus. At 37 degrees C, however, there was anomalous Scatchard binding behaviour at relatively higher concentrations of albumin (30 to 50 mg/ml) which could be due to either glomerular cell uptake or the appearance of multiple binding sites or both. The binding of albumin to isolated glomeruli and the glomerular albumin levels in isolated kidney perfusion could largely be accounted for by the binding of albumin to the glomerular basement membrane. The albumin binding to glomeruli at 37 degrees C was enhanced by Pronase digestion and heparinase digestion, but remained unchanged following trypsin treatment or neuraminidase treatment. Similarly, albumin was shown to bind to purified basement membrane preparations. This binding was also enhanced (approximately 80 times) by heparinase digestion but remained unchanged after digestion with chondroitinase ABC or hyaluronidase.(ABSTRACT TRUNCATED AT 250 WORDS)