Kinin

A kinin is any of various structurally related polypeptides, such as bradykinin and kallikrein. They are members of the autacoid family.

They act locally to induce vasodilation and contraction of smooth muscle.

It is a component of the kinin-kallikrein system.

Their precursors are kininogens.

In botany, plant hormones cytokinins were first called kinins, but the name was changed to avoid confusion.

Aspirin inhibits the activation of kallenogen by interfering with the formation of kallikrien enzyme which is essential in the process of activation.