Glycogen accumulation in renal tubules, a key morphological change in the diabetic rat kidney

Patients with diabetic nephropathy, characterised pathologically by glomerulosclerosis, may account for up to 40% of end-stage renal cases. The short-term (within 3 months) streptozotocin- or alloxan-induced rat model is often used but glomerulosclerosis is seldom reported and it is unclear what the primary renal lesions are. Diabetic rats were studied at 1, 3 and 6 months after a single injection of alloxan. Both methacrylate and paraffin-embedded renal sections were obtained and stained with PAS and haematoxylin. A morphometric study was performed with stereological methods to obtain the volumes and lengths or diameters of renal tubules and glomeruli. A key morphological change associated with sustained hyperglycaemia was the accumulation of glycogen granules in about half of the distal tubules and thin segments starting from 1 month after the experiment, which was then extended to about half of the proximal tubules at 6 months. Renal hypertrophy was seen with a 9% increase in the tubule diameter but not in the total length; glomerular morphology was basically unaffected. Further studies are needed to establish whether glomerulosclerosis would occur in longer term and whether this animal model would be appropriate to study the human condition of diabetes mellitus in terms of renal damage.