Age of onset of streptozocin diabetes determines the renal structural response in the rat.

Prepubertal years of insulin-dependent diabetes mellitus are protected from the nephropathic effects of this disease, yet this effect of immaturity has not been investigated in an animal model. Male Munich-Wistar rats were made diabetic with streptozocin at two ages: weanling (approximately 4 wk) and pubescent (approximately 10 wk). After 5 wk of untreated diabetes, weanling diabetic animals showed relatively greater growth of the medulla, whereas relative proportions of these areas were constant in the older animals. Glomerular volume increased by approximately 35% in older diabetic animals, but no glomerular enlargement was demonstrated in weanling rats with diabetes. Glomerular ultrastructure was not significantly altered during the short course of this study. The renal structural response to diabetes is age-dependent in the rat, with prepubertal animals protected from glomerular hypertrophy. Longer studies are needed to see if these differences will eventually parallel those demonstrated in patients with onset of diabetes before and after puberty. This model may ultimately prove to be valuable in determining the mechanism via which prepubertal kidneys are protected from the nephropathic effects of insulin-dependent diabetes mellitus.