Histamine content, diamine oxydase and histidine decarboxylase activities along the intestinal tract of the rat.

Histamine is widely distributed in the intestine where it is involved in many pathological reactions. The relations between histamine content, diamine oxidase and histidine decarboxylase activity have been investigated along rat's intestine. Results showed significant variations along the intestine. A correlation was observed between histamine and histidine decarboxylase (p less than 0.01), both of them being even in the small intestine (11.8 +/- 2.3 ng/mg ww and 112.5 +/- 21.2 fmoles/hr/mg ww respectively), significantly higher in the caecum (16.3 +/- 1.9 and 178 +/- 20.1) and significantly smaller in the colon (7.3 +/- 1.1 and 65.3 +/- 11.5) than in other intestinal segments. Diamine oxydase activity was higher in ileum (30.7 +/- 7.2 pmoles/min/mg ww) than in jejunum (17.1 +/- 2.8), caecum (4.3 +/- 0.8) and colon (2.6 +/- 2.7), and could not be linked to histamine content. The results fitted in the hypothesis that histamine in rat intestine is mainly located in mast cells where HDC is probably the main enzyme involved in its modulation.