人体中的硝酸盐生物合成
Nitrate biosynthesis in man.
作者信息
Green L C, Ruiz de Luzuriaga K, Wagner D A, Rand W, Istfan N, Young V R, Tannenbaum S R
出版信息
Proc Natl Acad Sci U S A. 1981 Dec;78(12):7764-8. doi: 10.1073/pnas.78.12.7764.
Nitrate metabolism was investigated in long-term metabolic studies in healthy young men. Under conditions of constant low ingestion of nitrate (less than 180 mumol/day per subject), the amount of nitrate excreted in urine was an average of 4-fold greater than the amount ingested. Balance studies with 15NO3- showed that the source of the excess nitrate in urine was the endogenous biosynthesis of nitrate, rather than the emptying of a body pool. Nitrate biosynthesis occurred when nitrate ingestion was high as well as low, and the amounts synthesized appeared to be independent of intake and comparable to the amounts ingested from normal diets. Analysis of the 15NO3- data also revealed that half of ingested nitrate was recovered as urinary nitrate. Because nitrate in urine is the net result of (i) intake, (ii) endogenous synthesis, and (iii) metabolic losses, the magnitude of the losses is such that, despite ongoing synthesis, the amount of nitrate in the urine of people consuming most diets will be less than the amount ingested.
在针对健康年轻男性的长期代谢研究中，对硝酸盐代谢进行了调查。在持续低剂量摄入硝酸盐的情况下（每位受试者每天摄入少于180微摩尔），尿液中排出的硝酸盐量平均比摄入量高4倍。用15NO3-进行的平衡研究表明，尿液中过量硝酸盐的来源是硝酸盐的内源性生物合成，而非体内储备的排空。当硝酸盐摄入量高或低时都会发生硝酸盐生物合成，合成量似乎与摄入量无关，且与正常饮食摄入的量相当。对15NO3-数据的分析还表明，摄入的硝酸盐中有一半以尿硝酸盐的形式回收。由于尿液中的硝酸盐是（i）摄入量、（ii）内源性合成和（iii）代谢损失的净结果，损失的程度使得尽管持续合成，但大多数饮食人群尿液中的硝酸盐量仍将少于摄入量。
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