kinin

one of a group of poly PEPTIDES that lower BLOOD PRESSURE through dilation of the BLOOD VESSELS and cause smooth MUSCLE to contract. They are associated with inflammation, causing local increases in the permeability of tissue capillaries (see CAPILLARY ). In addition they play some part in the allergic response and ANAPHYLAXIS . Kinins do not normally occur in the blood but form under these conditions or when the tissue is damaged (see also BRADYKININS ).