Zubair Ahmed - Academia.edu (original) (raw)
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Papers by Zubair Ahmed
Circulation Research, 2008
Reduction of nitrite (NO 2 − ) provides a major source of nitric oxide (NO) in the circulation, e... more Reduction of nitrite (NO 2 − ) provides a major source of nitric oxide (NO) in the circulation, especially in hypoxemic conditions. Our previous studies suggest that xanthine oxidoreductase (XOR) is an important nitrite reductase in the heart and kidney. Herein, we have demonstrated that conversion of nitrite to NO by blood vessels and RBCs was enhanced in the presence of the XOR substrate xanthine (10 μmol/L) and attenuated by the XOR inhibitor allopurinol (100 μmol/L) in acidic and hypoxic conditions only. Whereas endothelial nitric oxide synthase (eNOS) inhibition had no effect on vascular nitrite reductase activity, in RBCs L-NAME, L-NMMA, and l -arginine inhibited nitrite-derived NO production by >50% ( P <0.01) at pH 7.4 and 6.8 under hypoxic conditions. Western blot and immunohistochemical analysis of RBC membranes confirmed the presence of eNOS and abundant XOR on whole RBCs. Thus, XOR and eNOS are ideally situated on the membranes of RBCs and blood vessels to generate...
Circulation Research, 2008
Reduction of nitrite (NO 2 − ) provides a major source of nitric oxide (NO) in the circulation, e... more Reduction of nitrite (NO 2 − ) provides a major source of nitric oxide (NO) in the circulation, especially in hypoxemic conditions. Our previous studies suggest that xanthine oxidoreductase (XOR) is an important nitrite reductase in the heart and kidney. Herein, we have demonstrated that conversion of nitrite to NO by blood vessels and RBCs was enhanced in the presence of the XOR substrate xanthine (10 μmol/L) and attenuated by the XOR inhibitor allopurinol (100 μmol/L) in acidic and hypoxic conditions only. Whereas endothelial nitric oxide synthase (eNOS) inhibition had no effect on vascular nitrite reductase activity, in RBCs L-NAME, L-NMMA, and l -arginine inhibited nitrite-derived NO production by >50% ( P <0.01) at pH 7.4 and 6.8 under hypoxic conditions. Western blot and immunohistochemical analysis of RBC membranes confirmed the presence of eNOS and abundant XOR on whole RBCs. Thus, XOR and eNOS are ideally situated on the membranes of RBCs and blood vessels to generate...