Changes in the molecular sieve of glomerular basement membrane in rats with Masugi nephritis

Sprague-Dawley rats developed severe proteinuria 24 h after an intravenous injection with rabbit anti-rat kidney serum. Accumulation of polymorphonuclear leukocytes in the capillary lumen and their attachment to the glomerular basement membrane (GBM) were observed. The isolated and purified GBM of normal and nephritis-induced rats were observed by electron microscopy after negative staining. Although the GBM of normal rats appeared as a molecular sieve with uniform pores, the GBM of rats with nephritis had enlarged and elongated pores. An increase in the radius of glomerular pores may be responsible for the proteinuria.