The effect of spironolactone on renal histopathology. Representative light photomicrographs of Masson trichome stained sections from kidneys of (a,c) control and (b,d) 50 mg/kg per day spironolactone treated mice are shown. All of the mice exhibited evidence of proteinaceous, fuchsinophilic deposits in the subepithelial space with thickening of the capillary loops. The mesangium was also expanded in both groups but the cellularity was more commonly increased in the control animals (thin yellow arrow). In addition, the control mice had an active glomerulonephritis with prominent proliferation of extraglomerular cells forming crescents that have begun to organize (thick yellow arrows). Subendothelial deposits and hyaline thrombi were also much more commonly encountered in the control animals. Original magnification: 420× for panels a and b, and 840× for panels c and d.