Mesangial changes of the renal glomerulus in long-term diabetic rats.

The primitive morphological lesions of intercapillary glomerulosclerosis is not known but could be at the level of mesangial cells. The kidneys of nine long term (12 months) diabetic rats and seven controls were studied by electron microscopy. They showed the same kind of lesions as those described by Kimmelstiel in the kidneys of human diabetics: fine fibrillar or granular deposits in the cytoplasm of mesangial cells and an enlargement of the mesangial area by accumulation of membrane like material. The cytoplasmic inclusions resemble the basement membrane of the capillaries. At this stage there is no widening of the basement membrane of the capillaries. Thus, mesangial cell inclusions seem to be a precocious stage of the diabetic nephropathy and could result from an impairment of the capacity of the mesangial cell to catabolize the basement membrane.