May J M, Qu Z C, Xia L, Cobb C E
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6303, USA.
Am J Physiol Cell Physiol. 2000 Dec;279(6):C1946-54. doi: 10.1152/ajpcell.2000.279.6.C1946.
Nitric oxide, when released into the bloodstream, is quickly scavenged by Hb in erythrocytes or oxidized to nitrite. Nitrite can also enter erythrocytes and oxidize Hb. The goals of this work were to determine the mechanism of erythrocyte nitrite uptake and whether this uptake causes oxidant stress in these cells. Erythrocytes took up 0.8 mM nitrite with a half-time of 11 min. Nitrite uptake was sensitive to temperature and to the pH and ionic composition of the medium but was not inhibited by the specific anion-exchange inhibitor DIDS. About 25% of nitrite uptake occurred on the sodium-dependent phosphate transporter and the rest as diffusion of nitrous acid or other species across the plasma membrane. Methemoglobin formation increased in proportion to the intracellular nitrite concentration. Nitrite reacted with erythrocyte ascorbate, but ascorbate loading of cells decreased nitrite-induced methemoglobin formation only at high nitrite concentrations. In conclusion, nitrite rapidly enters erythrocytes and reacts with oxyhemoglobin but does not exert a strong oxidant stress on these cells.
一氧化氮释放到血液中后，会迅速被红细胞中的血红蛋白清除或氧化为亚硝酸盐。亚硝酸盐也可进入红细胞并氧化血红蛋白。本研究的目的是确定红细胞摄取亚硝酸盐的机制，以及这种摄取是否会在这些细胞中引起氧化应激。红细胞摄取0.8 mM亚硝酸盐的半衰期为11分钟。亚硝酸盐摄取对温度、培养基的pH值和离子组成敏感，但不受特异性阴离子交换抑制剂DIDS的抑制。约25%的亚硝酸盐摄取发生在钠依赖性磷酸盐转运体上，其余则是亚硝酸或其他物质跨质膜的扩散。高铁血红蛋白的形成与细胞内亚硝酸盐浓度成正比。亚硝酸盐与红细胞中的抗坏血酸反应，但只有在高亚硝酸盐浓度下，细胞内抗坏血酸的负载才会减少亚硝酸盐诱导的高铁血红蛋白形成。总之，亚硝酸盐迅速进入红细胞并与氧合血红蛋白反应，但不会对这些细胞施加强烈的氧化应激。
