Effects of aminoguanidine on structural alterations of microvessels in peripheral nerve of streptozotocin diabetic rats.

This study was designed to explore the effect of aminoguanidine (AG) on the structural abnormalities of microvessels in the sural nerve of streptozotocin-induced diabetic rats. Diabetic rats were treated with AG (25 mg/ kg, sc) for 16 weeks, a dose high enough to prevent glycation but also inhibit inducible nitric oxide synthase. Non-treated diabetic rats and normal Wistar rats were used for comparison. Morphometric analysis disclosed an expansion of vascular and luminal areas of endoneurial microvessels in diabetic rats, particularly of large size, compared to control rats. These changes were partially but significantly corrected by AG treatment. There was no closure of microvessels in diabetic rats. The mean ratio of basement membrane area to vascular area was significantly smaller in diabetic rats than that in normal control rats and basement membrane was not thickened in diabetic rats. The mean ratio of endothelial cell area to vascular area was smaller in diabetic rats than that in nondiabetic control rats, and it was not influenced by AG treatment. Numbers of microvessels per unit endoneurial area in diabetic rats were not different from those of control rats. These findings in conjunction with previous reports suggest that alterations of nerve blood flow detected in diabetic peripheral nerve may be relevant to structural alterations of endoneurial microvessels, which may be an early sign of endoneurial microangiopathy. We also consider that AG treatment is beneficial for experimental diabetic neuropathy, partially through the correction of endoneurial microcirculation.