[The effect of hyperglycemia on ischemic brain damage: relevance to the local cerebral blood flow]

The effect of hyperglycemia on ischemic brain damage in rats was studied by measuring the local cerebral blood flow (LCBF) using a transient middle artery (MCA) occlusion model. Rats, fasted except for water for 12-16 hours, were used. They were anesthetized with halothane and the stem of the left MCA was occluded for 2 hours by a microclip. Reperfusion was performed by removal of the clip. The rats were awaken from anesthesia after removal of the clip. Hyperglycemia was induced by intraperitoneal injection of 50% glucose and same volume of 50% D-mannitol or physiological saline were injected intraperitoneally 20 minutes before MCA occlusion in control rats. LCBF was measured by quantitative autoradiography using 14C-iodoantipyrine 2 hours after clipping and 2 hours after reperfusion. Some rats were prepared for neuropathological observation 72 hours after reperfusion. In hyperglycemic rats, plasma glucose concentration rose to over 500 mg/dl at the peak. A hyperglycemic state around 300 mg/dl was maintained during the experiments. Elevation of hematocrit and plasma osmolarity to the same degree were observed in both hyperglycemic and mannitol pretreated rats. On histological study ischemic neuronal cell damage was found to be more extensive in hyperglycemic rats than in the saline pretreated rats. At 2 hours after MCA occlusion, LCBF in the ischemic focus decreased significantly in hyperglycemic rats compared with the control. The reduction of LCBF was observed also in the contralateral non-ischemic side (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)