de Saint-Blanquat G
Ann Nutr Aliment. 1980;34(5-6):827-64.
The toxic action of nitrates and nitrites has often been summarized by methemoglobinemia and nitrosation of amines inducing carcinogenic effects; these two impacts are spectacular, but they hide varying more or less insidious actions recently studied and perceived. In the NO3/NO2 couple, it is accepted that especially nitrite ion lays down a toxicological problem, probably because of its particular chemical reactivity: nitrite ion, which is the base of nitrous acid HNO2 (pKa = 3.36) can react with many functional groups from dietary or endogenous origin; it is also a reducing agent, only oxidable by chemical oxidants or adequate enzyme systems; at the same time it is an oxidant for many reduced substrates. These different possibilities explain the chemical complexity of these compounds and almost their reactivity in biological various media with toxicological implications (modification of the redox state). In man, the presence of nitrates in the digestive tract may result in nitrite formation, because nitrate-reductase from bacterial or enterocyte origin; more particularly in stomach, nitrites are characterized by a great instability imputable to the low pH of gastric juice and to secreted factors which accelerate phenomena; at the same time, nitrates and nutrites exercise opposite effects on gastric secretion (volume, acidity, pepsin) and on gastric mucosal irrigation: while nitrates increase these different parameters, nitrites reduce secretory activity but correlations between secretion and irrigation show that nitrates induce a deep modification of hydric compartment whereas nitrites rather react through cellular anoxy. In intestine, nitrates and chiefly nitrites are very quickly absorbed by a passive mechanism and they are characterized by an extrahepatic cycle; nitrates and nitrites are also eliminated in large quantities by kidneys, and nitrates have a very high diuretic effect: these NO3- ions move Cl- ions, inducing a Na+ waste, a decrease in extracellular space and an alkalosis; this diuretic action of ionic origin is moreover increased by a rise in glomerular blood flow facilitating filtration; these compounds therefore present vasomotor effects, probably by an action on catecholamines whose metabolism is modified. Last, nitrates are suspected to be responsible for reproduction troubles, thyroid dysfunction, perturbances of vitamins availability and nutritional effects. Most of the impacts of nitrates and nitrites are now well known, but their cellular of molecular action is not clear, and as a result there is a suspicion in regard to these products very widely present in food.
硝酸盐和亚硝酸盐的毒性作用通常被概括为高铁血红蛋白血症以及胺类的亚硝化作用从而诱发致癌效应；这两种影响很显著，但它们掩盖了最近研究和认识到的各种或多或少较为隐匿的作用。在NO3/NO2组合中，人们普遍认为尤其是亚硝酸根离子引发了一个毒理学问题，这可能是由于其特殊的化学反应性：亚硝酸根离子是亚硝酸HNO2（pKa = 3.36）的碱，可以与许多来自饮食或内源性的官能团发生反应；它也是一种还原剂，只能被化学氧化剂或适当的酶系统氧化；同时它是许多还原底物的氧化剂。这些不同的可能性解释了这些化合物的化学复杂性以及它们在具有毒理学意义（氧化还原状态改变）的各种生物介质中的反应活性。在人体中，消化道中硝酸盐的存在可能导致亚硝酸盐的形成，这是因为细菌或肠细胞来源的硝酸还原酶；更特别的是在胃中，亚硝酸盐具有很大的不稳定性，这归因于胃液的低pH值和加速相关现象的分泌因子；同时，硝酸盐和亚硝酸盐对胃分泌（量、酸度、胃蛋白酶）和胃黏膜灌注具有相反的作用：虽然硝酸盐会增加这些不同参数，但亚硝酸盐会降低分泌活性，但分泌与灌注之间的相关性表明，硝酸盐会引起水相区室的深刻改变，而亚硝酸盐则主要通过细胞缺氧起反应。在肠道中，硝酸盐尤其是亚硝酸盐通过被动机制很快被吸收，并且它们具有肝外循环的特征；硝酸盐和亚硝酸盐也大量通过肾脏排出，并且硝酸盐具有很高的利尿作用：这些NO3-离子会带动Cl-离子，导致Na+流失、细胞外空间减少和碱中毒；这种离子源性的利尿作用还会因肾小球血流量增加促进滤过而增强；因此这些化合物可能通过对儿茶酚胺代谢产生改变的作用而呈现血管舒缩效应。最后，硝酸盐被怀疑与生殖问题、甲状腺功能障碍、维生素可利用性紊乱以及营养效应有关。硝酸盐和亚硝酸盐的大多数影响现在已广为人知，但它们的细胞或分子作用尚不清楚，因此人们对这些在食物中广泛存在的产品存在疑虑。
