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.

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