Characterisation of glucose transporters in the intact coronary artery endothelium in rats: GLUT-2 upregulated by long-term hyperglycaemia

Aims/hypothesis. We have examined the effects of streptozotocin-induced type 1 diabetes on the expression and subcellular distribution of the classic sugar transporters ( GLUT- 1 to 5 and sodium-dependent glucose transporter-1 [SGLT-1]) in the endothelial cells of an en face preparation of septal coronary artery from Wistar rats. Methods. The presence of the GLUT isoforms and SGLT-1 in the endothelial cell layer was determined by immunohistochemistry using wide-field fluorescence microscopy coupled to deconvolution, and was quantified by digital image analysis. Results. We found that all of the transporters were expressed within these cells and that all except SGLT-1 were preferentially located on the abluminal side. The heaviest labelling was adjacent to the cell-to-cell junctions where the luminal and abluminal membranes are in close proximity, which may reflect a spatial organisation specialised for vectorial glucose transport across the thinnest part of the cytoplasm. Long-term hyperglycaemia, induced by streptozotocin, significantly downregulated GLUT-1, 3, 4 and 5 and dramatically upregulated GLUT-2, leaving SGLT-1 unchanged. Conclusions/ interpretation. We conclude that the high susceptibility of endothelial cells to glucose toxicity may be the result of the subcellular organisation of their GLUTs and the increased expression of GLUT-2.