Assessment and topographical analysis of the total histamine degradation capacity (THDC) at the lower GI-tract

Aims: Irritable bowel syndrome (IBS) may cause various symptoms including abdominal pain, diarrhoea, constipation and is often associated with food intolerances.

Material and methods: To further evaluate the biological capacity of the GI-mucosa to degradate histamine 96 samples from the lower GI tract were homogenized and quantitative histamine degradation followed at different time points (0,8,12,20 min). Samples were taken from 24 patients with either IBS symptoms or known food allergy from ileum, cecum, colon ascendens and sigmoid. Histamine was measured by ELISA, THDC given as median (25 – 75%) ng histamine/mg protein x ml x min or % degradation.

Results: Endogenous histamine released from homogenized tissue was quantitatively catabolized within 20 min. The degradation kinetics showed a 50 ± 10% degradation rate already after 8 min and was two-staged. Interestingly, repeated experiments showed the THDC for terminal ileum 47,95 (22,07 – 74,70), followed by cecum 24,67 (16,63 – 37,70)) and colon ascendens median 23,73 (14,47 – 45,17)) respectively), while sigmoid had always the lowest histamine catabolization median 24,92 (13,71 – 35,40)). THDC was positively correlated to the number of lymphoid follicles at the lower gi tract.

Discussion: Measurement of the biological histamine degradation along the lower GI tract exhibited a topographical gradient for histamine catabolization with higher levels at the terminal ileum and cecum, followed by, to distal parts, decreasing values. Future studies will clarify whether disturbances of the histamine degradation in ileum or cecum may be associated with intestinal swelling, induction of inflammation or IBS symptoms.