Quantitative immunogold study of glucose transporter (GLUT-1) in five brain regions of scrapie-infected mice showing obesity and reduced glucose tolerance.

Distribution of glucose transporter (GLUT-1) in the microvascular endothelium of scrapie-infected SJL/J hyperglycemic mice showing clinical signs of scrapie, obesity and reduced glucose tolerance was studied in five brain regions: cerebral cortex, hippocampus, thalamus, cerebellum and olfactory bulb. Uninfected normoglycemic SJL/J mice showing normal glucose tolerance were used as a control. Ultrathin sections of brain samples embedded at low temperature in the hydrophilic resin Lowicryl K4M were exposed to anti-GLUT-1 antiserum followed by gold-labeled secondary antibodies. Labeling density was recorded over luminal and abluminal plasma membranes of microvascular endothelial cells. Ultrastructural observations revealed attenuation of the microvascular endothelial lining in numerous vascular profiles from brain samples of diabetic mice. Morphometric analysis revealed significant decreases of the labeling density for GLUT-1 in the microvasculature of the thalamus, cerebellum and, to a lesser degree, the hippocampus of diabetic mice. No significant differences between diabetic and non-diabetic, control mice were observed in the microvessels supplying cerebral cortex and olfactory bulb. These findings suggest that abnormal glucose metabolism, manifested by reduced glucose tolerance and hyperglycemia, leads to impaired transvascular glucose transport in some brain regions but not in others, presumably disturbing the function of those brain regions supplied by the affected blood microvessels.