Absorption and catabolism of histamine in sheep

Publisher Website
Google Scholar
Abstract
When 200 mg histamine diphosphate was administered into a rumen with normal contents the average time taken for the biological activity to disappear from the rumen was about 4 h. In sheep starved for 60 h the activity disappeared much more slowly. When 0.9% NaCl solution was substituted for the normal rumen contents and the rumen was isolated in situ under anesthesia, the disappearance of histamine was scarcely detectable. About 1% of the radioactivity introduced into such rumen preparations as [14C]histamine was recovered in the urine during a 6 h period. When both [14C]histamine and 200 mg unlabeled histamine diphosphate were administered into the rumen, between 4-15% of the radioactivity and 2-11% of the biological activity reached the duodenum. When jejunal loops isolated between 2 pairs of re-entrant cannulas were perfused with 0.9% NaCl solution containing histamine a considerable fraction of the histamine was absorbed from the loops. When [14C]histamine and 200 mg histamine diphosphate were administered into the rumen an average of 9% of the radioactivity appeared in the urine. When histamine was given into the abomasum the corresponding figure in a single experiment was 25%. Between 11-34% of the radioactivity administered into the rumen as [14C]histamine in the ruminoreticulum; the contribution of the intestines to 14CO2 was very small. When [3H]histamine was administered into the rumen most of the radioactivity in the urine a few days after administration was in the form of 3H2O water. The formation of 3H2O is probably a result of histamine metabolism in the fore-stomach, analogous to the formation of 14CO2.