Histamine uptake and metabolism in the blood vessels of rats

In vitro radiolabeled histamine uptake and metabolism were investigated in abdominal aorta, iliac artery, mesenteric artery and hepatic portal vein of the rat. Histamine uptake was rapid and remained linear over the initial 10 min of the accumulation period. The uptake rate was temperature sensitive with marked reduction in rate at 0°C. The accumulation at 0°C represents nonspecific uptake. The uptake of histamine was observed to be related to the amount of tissue stores of histamine as well as extracellular sodium ion concentration. The only histamine metabolite detected in the vasculature examined was imidazoleacetic acid representing almost 80% of the chromatogram radioactivity. This observation indicates the primary metabolic pathway for histamine in rat vasculature involves the enzyme, diamine oxidase.