CEREBRAL-ISCHEMIA ALTERS GLUCOSE-TRANSPORTER KINETICS ACROSS RAT-BRAIN MICROVASCULAR ENDOTHELIUM - QUANTITATIVE-ANALYSIS BY AN IN-SITU BRAIN PERFUSION METHOD

The purpose of this study was to quantify the changes of blood-brain b arrier glucose transporter kinetics following cerebral ischemia using an in situ brain perfusion technique. Sixty-four adult male Sprague-Da wley rats were divided into control and ischemia groups, and a four-ve ssel occlusion model was used to provide an ischemic insult. To obtain regional capillary permeability area products of glucose and regional perfusion fluid flow rates, the perfusion fluid was dually labeled wi th 2-deoxy[C-14]glucose and [H-3]diazepam, and the brain was perfused at a constant rate via the external carotid artery. After sampling tis sues from the brain, dual scintillation counting was performed and bot h regional perfusion fluid flow rates and regional capillary permeabil ity area products were calculated. We determined kinetic parameters, i ncluding V-max, K-m and K-d as described in the Michaelis-Menten equat ion, by the non-linear least squares method. In the ischemia group, a decrease in V-max and an increase in K-m were recognized, which mean d ecreases in the affinity and the number of functioning glucose transpo rters. These results suggest that cerebral ischemia downregulates the blood-brain barrier glucose transporters.