Exposure to elevated D-glucose concentrations modulates vascular endothelial cell vasodilatory response.

The possible role of endothelial dysfunction in early stages of uncomplicated diabetes mellitus was investigated in porcine aortic endothelial cells. Prolonged exposure to various D-glucose concentrations resulted in concentration-dependent amplification of agonist-induced Ca2+ mobilization, whereas L-glucose and D-mannitol failed to mimic the effect of D-glucose. This stimulatory effect of high D-glucose on endothelial Ca2+ mobilization could be antagonized by coincubation with cytochalasin B, which prevented D-glucose uptake into the cells. In agreement with its effect on agonist-induced Ca2+ response, prolonged preincubation with pathological D-glucose concentrations amplified formation of endothelium-derived relaxing factor, which is well established to be strictly attributable to increases in endothelial free Ca2+. In contrast to endothelium-derived relaxing factor formation stimulated by receptor-interacting autacoids, preincubation with high D-glucose failed to modulate A 23,187-induced endothelium-derived relaxing factor formation, which is attributable to unphysiological increases in endothelial free Ca2+ by this ionophore. Similar to its effect on D-glucose-mediated amplification of agonist-stimulated Ca2+ mobilization, cytochalasin B abolished the stimulatory effect of high D-glucose on endothelium-derived relaxing factor formation. We therefore suggest that prolonged exposure to pathological high D-glucose concentrations results in an enhanced endothelium-derived relaxing factor formation caused by amplification of agonist-stimulated Ca2+ mobilization in endothelial cells. This mechanism may be of particular importance representing a possible basis of pathological vasodilation and reduced peripheral resistance in early stages of diabetes mellitus.