Fate of orally administered histamine in rats

Abstract

Male and female adult albino rats fed on a histamine-free (< 0,1 /zg HB/g) diet were placed in metabolism cages, and both feces and uriníƒe collected separately during 2 days after a period of 3 days for adaptation; urinary and fecal histamine was estimated in 24 hours samples on isolated guinea-pig ileum. One mg of histamine was then administered by gastric catheter to every animal and samples collection continuated for 2 days more.

Total histamine in uriníƒe increased along the 24 hours following the oral administration of histamine, owing almost exclusively to conjugated histami­ne; free histamine undergoes only mi­nimal changes. This effect was more pronounced in females than in males. The amounts of histamine eliminated by this route were, respectively, 6 % and 2,5 % of the administered doses.

Histamine eliminated with feces during the 24 hours following its oral administraron represents the 20 % of the total in the case of females and the 10 % in the males. Considerable indivi­dual variations were observed, but it is evident that a great part of the ingested histaniine is not absorbed in the alimentary tract.

It is emphasized that the histamine in feces did not proceed from contamination with urine. The origin of fecal histamine when no histamine is given orally, is dicussed.