Analysis of N(alpha)-methylhistamine by gas chromatography-mass spectrometry.

A gas chromatography-electron capture mass spectrometry assay has been developed for the histamine H3 receptor agonist, N(alpha)-methylhistamine (N(alpha)-MH). The assay is linear from 50 pg-10 ng, with a limit of detection of 50 pg/ml for gastric juice and plasma, and 50 pg/sample for bacteria (10(7)-10(8) CFU) and gastric tissue (5-10 mg wet weight). The limits of quantification are 100 pg/ml for gastric juice (%RSD=1.4) and plasma (%RSD=9.4), and 100 pg/sample for bacteria (%RSD=3.9) and tissue (%RSD=5.8). N(alpha)-MH was not present in human plasma, but low levels (1.4 ng/ml and 0.4 ng/ml) were detected in two samples of human gastric juice obtained from patients infected with Helicobacter pylori.