Govoni Mirco, Jansson Emmelie A, Weitzberg Eddie, Lundberg Jon O
Department of Physiology and Pharmacology, Karolinska Institutet, Nanna Svartz väg 2, S-17177 Stockholm, Sweden.
Nitric Oxide. 2008 Dec;19(4):333-7. doi: 10.1016/j.niox.2008.08.003. Epub 2008 Aug 30.
Recent studies surprisingly show that dietary inorganic nitrate, abundant in vegetables, can be metabolized in vivo to form nitrite and then bioactive nitric oxide. A reduction in blood pressure was recently noted in healthy volunteers after dietary supplementation with nitrate; an effect consistent with formation of vasodilatory nitric oxide. Oral bacteria have been suggested to play a role in bioactivation of nitrate by first reducing it to the more reactive anion nitrite. In a cross-over designed study in seven healthy volunteers we examined the effects of a commercially available chlorhexidine-containing antibacterial mouthwash on salivary and plasma levels of nitrite measured after an oral intake of sodium nitrate (10mg/kg dissolved in water). In the control situation the salivary and plasma levels of nitrate and nitrite increased greatly after the nitrate load. Rinsing the mouth with the antibacterial mouthwash prior to the nitrate load had no effect on nitrate accumulation in saliva or plasma but abolished its conversion to nitrite in saliva and markedly attenuated the rise in plasma nitrite. We conclude that the acute increase in plasma nitrite seen after a nitrate load is critically dependent on nitrate reduction in the oral cavity by commensal bacteria. The removal of these bacteria with an antibacterial mouthwash will very likely attenuate the NO-dependent biological effects of dietary nitrate.
最近的研究出人意料地表明，蔬菜中富含的膳食无机硝酸盐可在体内代谢形成亚硝酸盐，进而生成具有生物活性的一氧化氮。最近有研究指出，健康志愿者在补充硝酸盐膳食后血压有所降低，这一效应与血管舒张性一氧化氮的形成相符。有观点认为口腔细菌在硝酸盐的生物活化过程中发挥作用，它们首先将硝酸盐还原为活性更高的阴离子亚硝酸盐。在一项针对7名健康志愿者的交叉设计研究中，我们检测了市售含氯己定抗菌漱口水对口服硝酸钠（10mg/kg溶于水）后唾液和血浆中亚硝酸盐水平的影响。在对照情况下，硝酸盐负荷后唾液和血浆中的硝酸盐和亚硝酸盐水平大幅升高。在硝酸盐负荷前用抗菌漱口水漱口对唾液或血浆中硝酸盐的积累没有影响，但消除了其在唾液中转化为亚硝酸盐的过程，并显著减弱了血浆中亚硝酸盐的升高。我们得出结论，硝酸盐负荷后血浆中亚硝酸盐的急性增加严重依赖口腔共生细菌对硝酸盐的还原作用。用抗菌漱口水清除这些细菌很可能会减弱膳食硝酸盐对一氧化氮相关生物学效应的影响。
