histamine

(his′tă-mĭn)

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(his′tă-mēn″)
C5H9N3; a substance produced from the amino acid histidine, which causes dilation of blood vessels, increased secretion of acid by the stomach, smooth muscle constriction (as in the bronchi), and mucus production, tissue swelling, and itching (during allergic reactions). Histamine is stored within mast cell granules.

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