BACKGROUND: A deficit in the endothelial production of nitric oxide (NO) is associated with the sequelae of reperfusion injury. Because endothelial NO synthesis depends on the cofactor tetra-hydrobiopterin (BH4), we hypothesized that depletion of this cofactor underlies the reduction of endothelium-dependent dilation in reperfusion injury. METHODS AND RESULTS: After occlusion of the left anterior descending coronary artery of a pig for 60 minutes followed by 90 minutes of reperfusion (ischemia/reperfusion), hearts were removed and the arterioles were isolated, cannulated, pressurized, and placed on an inverted microscope stage. Dose responses to the endothelium-independent dilator sodium nitroprusside and the endothelium-dependent dilators serotonin, A23187, and substance P were obtained under control conditions, after incubation with sepiapterin (intracellularly converted to BH4) or synthetic BH4 6-methyltetrahydropterin (MH4), and again after their washout. After ischemia/reperfusion, sodium nitroprusside maximally dilated arterioles (99 +/- 3%), whereas relaxation to serotonin, A23187, and substance P was significantly reduced (19 +/- 9%, 44 +/- 9%, and 54 +/- 8%, respectively). During incubation with sepiapterin (1 mumol/L) or MH4 (10 mumol/L), endothelium-dependent dilation was significantly enhanced (P < .05), whereas the response to sodium nitroprusside was unaltered. After washout, the vasodilatory responses were not significantly different from the initial ischemia/reperfusion responses. Sepiapterin and MH4 did not affect vasodilatory responses in vessels obtained from nonischemic control hearts. As after ischemia/reperfusion, incubation of control vessels with 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP cyclohydrolase I, decreased endothelium-dependent vasodilation, which was restored in the presence of sepiapterin or MH4. CONCLUSIONS: These data indicate that exogenous administration of sepiapterin or MH4 restores the response to endothelium-dependent vasodilators in pig coronary arterioles after ischemia/ reperfusion. We therefore conclude that ischemia/reperfusion alters the availability or production of BH4, which contributes to blunted endothelial nitroxidergic vasodilation.
BACKGROUND: A deficit in the endothelial production of nitric oxide (NO) is associated with the sequelae of reperfusion injury. Because endothelial NO synthesis depends on the cofactor tetra-hydrobiopterin (BH4), we hypothesized that depletion of this cofactor underlies the reduction of endothelium-dependent dilation in reperfusion injury. METHODS AND RESULTS: After occlusion of the left anterior descending coronary artery of a pig for 60 minutes followed by 90 minutes of reperfusion (ischemia/reperfusion), hearts were removed and the arterioles were isolated, cannulated, pressurized, and placed on an inverted microscope stage. Dose responses to the endothelium-independent dilator sodium nitroprusside and the endothelium-dependent dilators serotonin, A23187, and substance P were obtained under control conditions, after incubation with sepiapterin (intracellularly converted to BH4) or synthetic BH4 6-methyltetrahydropterin (MH4), and again after their washout. After ischemia/reperfusion, sodium nitroprusside maximally dilated arterioles (99 +/- 3%), whereas relaxation to serotonin, A23187, and substance P was significantly reduced (19 +/- 9%, 44 +/- 9%, and 54 +/- 8%, respectively). During incubation with sepiapterin (1 mumol/L) or MH4 (10 mumol/L), endothelium-dependent dilation was significantly enhanced (P < .05), whereas the response to sodium nitroprusside was unaltered. After washout, the vasodilatory responses were not significantly different from the initial ischemia/reperfusion responses. Sepiapterin and MH4 did not affect vasodilatory responses in vessels obtained from nonischemic control hearts. As after ischemia/reperfusion, incubation of control vessels with 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP cyclohydrolase I, decreased endothelium-dependent vasodilation, which was restored in the presence of sepiapterin or MH4. CONCLUSIONS: These data indicate that exogenous administration of sepiapterin or MH4 restores the response to endothelium-dependent vasodilators in pig coronary arterioles after ischemia/ reperfusion. We therefore conclude that ischemia/reperfusion alters the availability or production of BH4, which contributes to blunted endothelial nitroxidergic vasodilation.
Authors: Jianzhong An; Jianhai Du; Na Wei; Hao Xu; Kirkwood A Pritchard; Yang Shi Journal: Am J Physiol Heart Circ Physiol Date: 2009-08-28 Impact factor: 4.733
Authors: Jane Chun-wen Teng; Helen Kay; Qian Chen; Jovan S Adams; Christopher Grilli; Giuseppe Guglielmello; Christopher Zambrano; Samuel Krass; Adrian Bell; Lindon H Young Journal: Naunyn Schmiedebergs Arch Pharmacol Date: 2008-05-22 Impact factor: 3.000