Tubular lesions in streptozotocin-diabetic rats.

Renal tubular lesions have been studied in streptozotocin-diabetic rats after 50 days of diabetes and compared with age-matched controls. The kidney weight increased by 67% in the diabetic animals and the length of the proximal tubules increased by 22%, but no abnormalities were found. The length of the distal tubules increased by 20% and the total increase was due to abnormal distal tubules. These abnormalities were confined to the cortex and the outer stripe of the outer medulla, but they were not seen in the inner stripe of the outer medulla. Abnormal cells were found also in the distal tubular cells of the macula densa. The total length of the collecting ducts was the same in the two groups and the cells appeared normal. The cells of the abnormal distal tubules appeared either empty or full of a PAS-positive material, digestable with alpha-amylase. At the electron microscope level, the cytoplasm of the cells contained glycogen-like granules, strikingly few organelles and the basal infoldings were greatly reduced. It is suggested that these tubular lesions might play a role in the development of renal functional changes in diabetes.