COMPARISON OF HYALINE DROPLETS IN RATS WITH CHRONIC PROGRESSIVE NEPHROPATHY AND CHEMICAL-INDUCED α2u-GLOBULIN NEPHROPATHY

Hyaline droplets in kidney tubules of rats with chronic progressive nephropathy were histopathologically compared with those found in 2, 2, 4-trimethylpentane (TMP) induced α2u-globulin nephropathy. Repeated oral administration of TMP at the dosage of 50 mg/kg/day for four weeks caused development of hyaline droplets which were all immunohistochemically positive for α2u-globulin. In control rats (13 to 52 weeks-old), two types of hyaline droplets were observed : one small round and multiple type being deeply eosinophilic and refractile (hyaline droplet type) ; and the other being slightly eosinophilic, large, and generally single (eosinophilic body type) . Both were positive for anti-α2u-globulin immunohistochemical staining. Fifty-two and 109 weeks-old male rats with chronic progressive nephropathy showed "hyaline droplet degeneration" of tubules with hyaline cast formation in the lumina. Immunohistochemical examination revealed such "hyaline droplet degeneration" to be positive for albumin, but negative for α2u-globulin. Under the electron microscope, round, amorphous, and moderately electron-dense phagolysosomes were observed in the tubules of "hyaline droplet degeneration" cases, clearly different from the polyangular and crystalline-like electron-dense phagolysosomes of normal α2u-globulin reabsorption droplets in young rats or TMP induced α2u-globulin accumulation droplets. The present results suggest that the etiology of chronic progressive nephropathy may be somewhat different from that of α2u-globulin induced nephropathy in terms of the causative protein.