A fast histochemical staining method to identify hyaline droplets in the rat kidney.

Hyaline droplet formation in the proximal tubular cells of the kidney commonly occurs under different pathological conditions in experimental animals. In rats, intracytoplasmic hyaline droplet formation is predominantly associated with accumulation of the male rat-specific alpha(2u)-globulin, whereas under other (pathological) conditions (eg, histiocytic sarcoma and chronic progressive nephropathy [CPN]) other proteins are involved. Staining methods to visualize hyaline droplets either need plastic embedded material or time-consuming (immuno)histochemical methods. A fast Chromotrope-Aniline-Blue-staining on formalin-fixed paraffin-embedded kidneys taking only 30 minutes is described. Using this method, hyaline droplets consisting of different types of proteins are easily recognized by their bright-red color.