Mild hyperglycemia and insulin treatment in experimental cerebral ischemia in rats

We investigated the effects of mild hyperglycemia and insulin treatment on the metabolism of the ischemic brain in spontaneously hypertensive rats with acute hyperglycemia (n = 9), acute hyperglycemia treated with insulin during ischemia (n = 10), and normoglycemia (n = 10). Cerebral blood flow was measured by the H2 clearance method. Cerebral ischemia induced by occlusion of the bilateral carotid arteries. Cerebral glycolytic metabolites were measured enzymatically. Blood glucose levels were significantly higher in hyperglycemic animals (11.8 to 13.7 mM/l) than in normoglycemic animals (6.0 mM/l). At 60 min of ischemia, the blood flow to the parietal cortex was decreased to 3% of the resting value in all groups. Blood glucose levels at 60 min of ischemia in the hyperglycemic rats were 1.9--3 times higher than the treated hyperglycemic rats and normo-glycemic rats. Glucose concentrations were significantly and positively correlated with the ATP level (p < .0001) but not with the lactate levels in the ischemic brain. Our results suggest that mild hyperglycemia may preserve glucose metabolism in the presence of ischemic insult.