A group of endogenous polypeptides, including kallidin, bradykinin, angiotensin, and substance P, which cause smooth muscle to contract. They also act as powerful vasodilators, lowering blood pressure. They are not normally present in the blood, but occur, for example. when tissue is damaged. Kinins are thought to play a role in the inflammatory response and may contribute to ischaemic pain.

The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.