Laboratory of Physical Chemistry, Department of Chemistry, University of Helsinki, Finland.
J Breath Res. 2013 Mar;7(1):017109. doi: 10.1088/1752-7155/7/1/017109. Epub 2013 Feb 27.
Ammonia concentrations in exhaled breath (eNH3) and skin gas of 20 healthy subjects were measured on-line with a commercial cavity ring-down spectrometer and compared to saliva pH and plasma ammonium ion (NH(+)4), urea and creatinine concentrations. Special attention was given to mouth, nose and skin sampling procedures and the accurate quantification of ammonia in humid gas samples. The obtained median concentrations were 688 parts per billion by volume (ppbv) for mouth-eNH3, 34 ppbv for nose-eNH3, and 21 ppbv for both mouth- and nose-eNH3 after an acidic mouth wash (MW). The median ammonia emission rate from the lower forearm was 0.3 ng cm(-2) min(-1). Statistically significant (p < 0.05) correlations between the breath, skin and plasma ammonia/ammonium concentrations were not found. However, mouth-eNH3 strongly (p < 0.001) correlated with saliva pH. This dependence was also observed in detailed measurements of the diurnal variation and the response of eNH3 to the acidic MW. It is concluded that eNH3 as such does not reflect plasma but saliva and airway mucus NH(+)4 concentrations and is affected by saliva and airway mucus pH. After normalization with saliva pH using the Henderson-Hasselbalch equation, mouth-eNH3 correlated with plasma NH(+)4, which points to saliva and plasma NH(+)4 being linked via hydrolysis of salivary urea.
20 名健康受试者的呼出气（eNH3）和皮肤气中的氨浓度采用商业腔衰减光谱仪进行在线测量，并与唾液 pH 值和血浆铵离子（NH(+)4）、尿素和肌酐浓度进行比较。特别关注了口腔、鼻腔和皮肤采样程序以及潮湿气体样品中氨的准确定量。获得的中位数浓度分别为 688 体积份每十亿份（ppbv）的口腔 eNH3、34 ppbv 的鼻腔 eNH3、以及酸性口腔冲洗（MW）后口腔和鼻腔 eNH3 的 21 ppbv。前臂下侧的氨排放率为 0.3ng cm(-2) min(-1)。呼吸、皮肤和血浆氨/铵浓度之间没有发现统计学上显著的（p < 0.05）相关性。然而，口腔 eNH3 与唾液 pH 值具有强烈的相关性（p < 0.001）。这种依赖性也在 eNH3 的昼夜变化和对酸性 MW 的响应的详细测量中观察到。因此得出结论，eNH3 本身不能反映血浆，而是反映唾液和气道黏液 NH(+)4 浓度，并且受到唾液和气道黏液 pH 值的影响。使用 Henderson-Hasselbalch 方程将 eNH3 与唾液 pH 值进行归一化后，口腔 eNH3 与血浆 NH(+)4 相关，这表明唾液和血浆 NH(+)4 通过唾液尿素的水解而相互关联。
