Estimate of production of gaseous nitrogen in the human body based on ~(15)N analysis of breath N_2 after administration of[~(15)N_2]urea: Dedicated to Professor Dr habil. Hans Faust on the occasion of his 85th birthday

摘要

After oral administration of [~(15)N_2]urea (1.5 mmol, 95 atom% ~(15)N), we found that breath N_2 was significantly ~(15)N-labelled. The result suggests that molecular nitrogen in breath must be partly produced endogenously. Based on a metabolic model, the endogenous N_2 production was estimated to be 0.40 ± 0.25 mmol kg~(-1) d~(-1) or 2.9 ± 1.8 % of the total (urinary and faecal) N excretion in fasted healthy subjects (n = 4). In patients infected with Helicobacter pylori (n - 5), the endogenous N_2 production was increased to 1.24 ± 0.59 mmol kg~(-1) d~(-1) or 9.0 ± 4.3 % of the total N excretion compared to the healthy controls (p ＜ 0.05). We conclude that N balance and gas exchange measurements may be affected by endogenously produced nitrogen, especially in metabolic situations with elevated nitrosation, for instance in oxidative and nitrosative stress-related diseases such as H. pylori infections.