Glomerular permeability to endogenous proteins in the rat: effects of acute hypertension.

The distribution of endogenous albumin and immunoglobulin G (IgG) has been studied by the immunoperoxidase technique in the superficial glomeruli of both normotensive and hypertensive (acute angiotensin II-induced) Munich-Wistar rats. Endogenous IgG has also been detected in rats immunized with horseradish peroxidase. Labeled antibodies have been applied to sections on a conventional manner as well as by an electrophoretic technique. The immunization of animals with horseradish peroxidase, as well as application of the electrophoretic technique, both result in a greater yield of labeled glomeruli. Albumin is present within the capillary lumina of control animals, penetrates the capillary walls, and extends into the urinary space. Endogenous IgG is mainly confined to lumina of glomerular capillaries, with only small amounts visible in the laminae rarae of the basement membrane. After acute hypertension induced by angiotensin II, there is increased staining of albumin and IgG in the basement membrane and of albumin in the urinary space. There is also penetration of IgG into Bowman's space. Both macromolecules are found in dilated mesangial channels. These modifications of glomerular permselectivity in hypertension are not accompanied by discernible ultrastructural changes in the peripheral capillary wall. It is suggested that the transcapillary passage of albumin and IgG is dependent upon hemodynamic factors and/or subtle changes in the filtering membrane.