Bradykinin (BK) (from Greek brady- 'slow' + -kinin, kīn(eîn) 'to move') is a peptide that promotes inflammation. It causes arterioles to dilate (enlarge) via the release of prostacyclin, nitric oxide, and endothelium-derived hyperpolarizing factor, and makes veins constrict via prostaglandin F2, thereby leading to leakage into capillary beds due to the increased pressure in the capillaries. Bradykinin consists of nine amino acids, and is a physiologically and pharmacologically active peptide of the kinin group of proteins.
A class of drugs called angiotensin-converting-enzyme inhibitors (ACE inhibitors) increase bradykinin levels by inhibiting its degradation, thereby increasing its blood pressure-lowering effect. ACE inhibitors are used to treat hypertension and heart failure.