Suzuki H, Moriya A, Iijima K, McElroy K, Fyfe V E, McColl K E L
Division of Gastroenterology, Gardiner Institute, Western Infirmary, Glasgow, Scotland.
Scand J Gastroenterol. 2003 Aug;38(8):856-63. doi: 10.1080/00365520310004119.
We have examined the suitability of microdialysis probes for examining nitrosative chemistry within localized regions of the lumen of the gastrointestinal tract. Chemical nitrosation occurs maximally at pH 2.5 in the presence of nitrite and thiocyanate and absence of ascorbic acid. Nitrite and thiocyanate are delivered into the stomach in saliva and ascorbic acid is secreted in gastric juice.
We used a benchtop model to reproduce the nitrosative chemistry occurring in the human upper GI tract and assessed the ability of the microdialysis probes to measure it.
The microdialysis probes were reliable at measuring nitrite ascorbic acid, total vitamin C and thiocyanate in both aqueous solutions and human gastric juice over the full range of intragastric pH, i.e. 1.5, 2.5, 3.5, 5.0 and 7.0. The probes were also reliable at measuring these chemicals under conditions simulating the active interaction between nitrite and ascorbic acid. Under such conditions with ascorbic acid in excess the probes gave a more accurate assessment of the nitrite level than that obtained by directly sampling the gastric juice. This was due to the probes not being subject to artefactual measurement of nitric oxide as nitrite. This was prevented by the rapid diffusion of nitric oxide through the probe collecting tube.
Microdialysis probes provide a reliable means of examining nitrosative chemistry within the lumen of the upper GI tract. In addition, they have the advantage of measuring this chemistry in very local regions and of simultaneously comparing the chemistry in different regions of the upper GI tract.
我们研究了微透析探针用于检测胃肠道管腔局部区域内亚硝化化学过程的适用性。在存在亚硝酸盐和硫氰酸盐且不存在抗坏血酸的情况下，化学亚硝化作用在pH 2.5时达到最大值。亚硝酸盐和硫氰酸盐通过唾液进入胃内，而抗坏血酸则由胃液分泌。
我们使用台式模型来重现人类上消化道中发生的亚硝化化学过程，并评估微透析探针测量该过程的能力。
在胃内pH值的整个范围内，即1.5、2.5、3.5、5.0和7.0时，微透析探针在测量水溶液和人胃液中的亚硝酸盐、抗坏血酸、总维生素C和硫氰酸盐方面是可靠的。在模拟亚硝酸盐与抗坏血酸之间活性相互作用的条件下，这些探针在测量这些化学物质时也很可靠。在抗坏血酸过量的这种条件下，与直接采集胃液相比，探针能更准确地评估亚硝酸盐水平。这是因为探针不会将一氧化氮误测为亚硝酸盐。一氧化氮通过探针收集管的快速扩散防止了这种误测。
微透析探针为检测上消化道管腔内的亚硝化化学过程提供了一种可靠的方法。此外，它们具有在非常局部的区域测量这种化学过程以及同时比较上消化道不同区域化学过程的优势。
