Structural distortion of glomerular capillary loops in the chronic phase of rat Masugi nephritis.

Structural distortion of glomerular capillaries in chronic rat Masugi nephritis was studied by light, transmission electron, and scanning electron microscopy. A few months after rats were given injections of heterologous nephrotoxic antibodies, focal and local mesangial as well as basement membrane thickenings were observed. Using scanning electron microscopy, glomerular corrosion castings disclosed that definite loop constriction with occasional gaps occurred in such local foci. The local changes were gradually extended to adjacent areas in rats with severe proteinuria, later resulting in a broad disappearance of the loops. Also observed were glomeruli undergoing a collapse with structural simplification resulting from multiple loss of communicating branches. At the terminal stage, almost all glomeruli were involved in varying degrees in either of these changes. In contrast, no progression of the disease process was observed in rats with minimal proteinuria. By scanning electron microscopy, a large number of castings from various angles revealed that morphologically normal glomeruli were involved in local and ultimately global obsolescence under the condition of persistent proteinuria.