Examination of the serosal fluid following in vitro luminal perfusion of rat intestinal segments with 1 mg/ml [3H]histamine for 2 hr showed that histamine constituted only 22.1% of the total serosal radioactivity. The remainder of the radioactivity was comprised of histamine metabolites. When equimolar amounts of either aminoguanidine and cadaverine were added to the luminal perfusate, the percentage of the serosal radioactivity as histamine increased to 67.0 and 60.4%, respectively. However, when equal amounts of histamine and anserine were added to the luminal perfusate, only 30.6% of the 3H translocated within 2 hr was [3H]histamine. In all cases, the gross translocation rate based on the percentage of total serosal radioactivity for total radioisotope ([3H]histamine plus [3H]histamine metabolites) was unchanged by the addition of these substances to the luminal perfusate. The results indicate that the potentiation of histamine toxicity by putrefactive amines, such as cadaverine, results from the inhibition of histamine metabolism which leads to increased uptake of unmetabolized histamine. The results do not support the hypothesis that potentiation occurs via an overall increase in the absorption of histamine and its metabolites due to some disruption in the barrier function of the intestine.
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