Abstract
The kidneys of 39 wild Norway rats (Rattus noryegicus), 9 months or older, were examined for evidence of chronic progressive nephrosis, which commonly affects year-old albino rats. An infectious process resembling pyelonephritis was found in two rats. Protein absorption droplets, intranuclear inclusion bodies resembling those of lead intoxication, and large ‘aberrant’ nuclei were seen in the epithelial cells of the proximal convolutions. The nematode, Trichosomoides crassicauda, was found in the renal pelvis of approximately one fourth of the rats. Basement membranes of the glomerular tufts, Bowman's capsule and proximal tubule were examined in four rats by electron microscopy. The mean thickness of basement membranes of peripheral glomerular loops was 0.28 ± 0.09 μm, which is comparable to that of young healthy Sprague-Dawley rats. The protein content in 65 determinations of 24-hour serial collections of urine ranged from less than 1 to 3.9 mg/ml. No tendency was observed toward increased protein excretion or progressive deterioration of the kidneys, such as occurs in older Sprague-Dawley rats.