Ultrastructural study of nephritis induced in Brown Norway rats by mercuric chloride

Chronic intoxication by mercuric chloride induces a two-phased nephropathy in Brown Norway rats characterized at first by a linear fixation of antiglomerular basement membrane antibody, then by a granular arteriolar and glomerular fixation of IgG superimposed on the linear one. On the 8th and 9th days, concomitant with the glomerular fixation of antiglomerular basement membrane antibodies, electron microscopy studies demonstrated an influx of monocytes into the glomerular and interstitial capillaries and a focal detachment of the glomerular endothelial cells. On the 14th and 15th days, subendothelial heterogeneous material and scattered subepithelial deposits appeared in glomeruli. By the 60th day, no cellular infiltration nor glomerular endothelial alterations persisted. Subepithelial glomerular deposits were seen in half of the animals, and abnormal deposits situated between muscular cells of the arteriolar walls were seen in all of them. These observations suggest that the glomerular fixation of antiglomerular basement membrane antibodies induces transient alterations of the inner aspect of the glomerular capillary wall. Arteriolar and subepithelial glomerular deposits confirm the idea that an immune-complex disease replaces the antiglomerular basement membrane antibody-mediated process. The morphologic expression of the transition between these two mechanisms is evident around the 15th day.