Abstract
Hypoglycemia induced by injection of insulin leads to dysfunction of the central nervous system. However, there have been few studies on the changes in ultrastructure of the cerebral vascular system caused by the hypoglycemia. In the present study, we investigated the ultrastructure of the cerebral arterial endothelium using scanning (SEM) and transmission electron microscpy (TEM), in male Wistar rats of normal blood pressure and spontaneously hypertensive rats (SHR) which were treated with insulin (Actrapid, 1.0 unit/100g body weight).
1) The death rate from hypoglycemic convulsions in SHR was 100.0%, which was significantly higher than that of normal rats, 16.7%.
2) SEM observations of the luminal surface of the middle cerebral artery revealed that there were ultrastructural differences in the microvilli and marginal folds of the endothelium between intact normal rats and intact SHR.
3) Injection of insulin caused detachment or disappearance of the endothelium and the occurrence of craters along the marginal folds in both groups. The damage was more prominent in SHR.
4) TEM observations revealed that there were some damaged endothelial cells whose cytoplasmic ultrastructure had been mostly lost in insulin-treated rats. Leakage of red blood cells into the extravascular space was also observed. Fifty-five % of the red blood cells had an unhomogeneous stroma.
These results suggest that insulin-induced hypoglycemia causes ultrastructural damage of the cerebral arterial endothelium, leakage of blood components through the marginal folds and bleeding, and that such damage is more remarkable in SHR.
