Veterinary Neuropharmacology

KININS

• Kinins are local mediators of pain and inflammation.
• The kinins are a family of small peptide molecules, which include: Bradykinin and Kallidin.
• Tissue damage, allergic reactions, viral infections and inflammatory events activate a series of proteolytic reactions and liberate bradykinin and kallidin.
• These agents act locally to produce pain, vasodilatation, increased vascular permeability and synthesize prostaglandins.
• When urine was injected intravenously there was a reduction in blood pressure.
• Same response was noticed when saliva, plasma and a variety of tissues.
• Pancreas was identified as the organ with rich source of this blood pressure lowering agent. Hence, they were termed as Kallikreins.
• Plasma kinins are polypeptides that split off from a plasma globulin kininogen by the action of specific enzymes kallikreins. It was noticed that trypsin and certain snake venoms acted on plasma globulin to produce a substance that lowered blood pressure and caused a slow developing contraction of the gut. Because of this slow response this substance was termed as bradykinin (brady – slow, kinin – to move).
• kallidin, a decapeptide was identified with almost similar actions. Thereafter a number of polypeptides with similar pharmacological actions were identified in nature. All these substances together were termed as kinins. Bradykinin and kallidin were termed as plasma kinins.