Increase in glucose transporter densities of Glut3 and decrease of glucoseutilization in rat brain after one week of hypoglycemia

The present study addresses the question whether a chronic decrease of plas ma glucose concentration for 1 week induces a global or local increase in g lucose transporter densities Glut1 and Glut3 in the brain. To induce chroni c hypoglycemia insulin was infused into rats by osmotic minipumps for 1 wee k resulting in a mean plasma glucose concentration of 3.1 +/- 0.5 mmol/l (c ontrol group: 8.1 +/- 0.5 mmol/l). Global and local densities of Glut1 and Glut3 glucose transporters were measured by immunoautoradiographic methods. The mean density of glucose transporters Glut1 remained unchanged, whereas the mean density of Glut3 increased slightly, although significantly. To d etermine whether the increased density of Glut3 is related to a change in g lucose metabolism, the local cerebral metabolic rate of glucose (ICMRglc) w as quantified by the 2-deoxyglucose method. Mean glucose utilization was de creased by 15%. Local analysis of transporter densities (Glut1 and Glut3) a nd glucose utilization showed a significant correlation between local gluco se transporter densities (Glut1 and Glut3) and ICMRglc during hypoglycemia as already previously observed during normoglycemia. It is concluded that 1 week of hypoglycemia is a stimulus for the induction of additional glucose transporters Glut3 in the brain. These additional neuronal glucose transpo rters may support the maintenance of glucose utilization which is not compl etely maintained under these conditions. (C) 1999 Elsevier Science B.V. All rights reserved.