Impairment of endothelial nitric oxide production by acute glucose overload

We examined the effects of acute glucose overload (pretreatment for 3 h with 23 mM D-glucose) on the cellular productivity of nitric oxide (NO) in bovine aortic endothelial cells (BAEC). We had previously reported (Kimura C, Oike M, and Ito Y. Circ Res, 82: 677-685, 1998) that glucose overload impairs Ca²⁺ mobilization due to an accumulation of superoxide anions (O₂^-) in BAEC. In control cells, ATP induced an increase in NO production, assessed by diaminofluorescein 2 (DAF-2), an NO-sensitive fluorescent dye, mainly due to Ca²⁺ entry. In contrast, ATP-induced increase in DAF-2 fluorescence was impaired by glucose overload, which was restored by superoxide dismutase, but not by catalase or deferoxamine. Furthermore, pyrogallol, an O₂^- donor, also attenuated ATP-induced increase in DAF-2 fluorescence. In contrast, a nonspecific intracellular Ca²⁺ concentration increase induced by the Ca²⁺ ionophore A-23187, which depletes the intracellular store sites, elevated DAF-2 fluorescence in both control and high D-glucose-treated cells in Ca²⁺-free solution. These results indicate that glucose overload impairs NO production by the O₂^--mediated attenuation of Ca²⁺ entry.