Characteristics of Histamine Disposition in Vascular Smooth Muscle

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Abstract
This study has examined uptake, efflux and metabolism of 14C-histamine by vascular smooth muscle. 14C space in aortae reached 4.3 ± 0.14 ml/g (mean ± SE) after 1 h exposure to 14C-histamine (2 μM) in Tyrode’s solution. Aminoguanidine (10–5M) and non-radioactive histamine (10–4 and 10–3M) significantly reduced 14C space. Efflux experiments were performed on aortic strips exposed to 14C-histamine for 1 h. The rate of loss of radioactivity was not enhanced by nonradioactive histamine or compound 48/80. It appears that 14C-histamine was not accumulated and bound in mast cells in this tissue. After 1 h exposure to 14 C-histamine, labeled material was extracted from tissues for identification of metabolites by paper chromatography. About 40 % of the label was 14C-histamine, and the remainder was primarily imidazole acetic acid. After exposure to aminoguanidine, an inhibitor of diamine oxidase, about 80 % of the label was 14C-histamine. These data suggest that oxidative deamination is the primary catabolic route for histamine in rabbit aorta.

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