Definition

A nonapeptide messenger that is enzymatically produced from KALLIDIN in the blood where it is a potent but short-lived agent of arteriolar dilation and increased capillary permeability. Bradykinin is also released from MAST CELLS during asthma attacks, from gut walls as a gastrointestinal vasodilator, from damaged tissues as a pain signal, and may be a neurotransmitter. Bradykinin is a vasoactive kinin that is liberated from its substrate kininogen by the action of kallikrein, and is known to be involved in a wide range of biologic processes. It may play an important role in blood pressure regulation and the maintenance of normal blood flow. Moreover, in various pathologic states of the cardiovascular system, it appears to provide protective actions against ischemic injury, ventricular hypertrophy, congestive heart failure, and thrombosis. Bradykinin is a potent vasodilator that acts through endothelial B2 kinin receptors to stimulate the release of nitric oxide and endothelium-derived hyperpolarizing factor. Bradykinin deficiency states may play a role in some forms of hypertension, and a relative deficiency in bradykinin may be a contributing factor to worsening heart failure. Experimental studies revealed that mice lacking the B2 receptor gene were more likely to develop hypertension, cardiac hypertrophy, and myocardial damage. Kinins exert several biologic actions. They are involved in nociception, inflammation, capillary permeability, reactive hyperemia, and stimulation of cellular glucose uptake. Bradykinin is a polypeptide that circulates in the plasma in very low concentrations in comparison with the amount of bradykinin found in various body tissues. Kininogens ([alpha] 2 globulins) are synthesized in the liver and circulate at high concentrations in the plasma. There are two kininogenases that convert kininogens into bradykinin: plasma kallikrein, also known as Fletcher factor, and glandular kallikrein, also known as tissue kallikrein. (PMID: 11975815) [HMDB]

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