Kallikrein-Kinin system

1. Kallikrein-Kinin system They are hormones activated by noxious stimuli to participate in tissue defense and repair. The kinins are peptides of 9-11 amino acids generated from plasma proteins called kininogens by specific proteases called kallikreins Kallikreins are present in plasma and organs Produces bradykinin short- lived vasoactive peptide Increases vascular permeability, Pain producer and potent smooth muscle dilator.

2. Kallikreins They originate from liver plasma kallikreins exocrine glands glandular kallikreins from the kidney They are responsible for the formation of kinins They exist as prekallikreins activated by chemical and physical factors.

3. Effects of Kinins Vascular Effects: potent vasodilators Inflammatory effects: promote release of prostglandins, prostacyclins and histamins. Implicated in tissue reaction to injury and repair by Stimulating mitosis of T-lymphocytes and protein formation Algogenic effect: they produce pain Stimulate release of catecholamines from the adrenal gland. Stimulate renin from kidney. Kinins induce natriuresis and duiresis. They antagonize the effect of ADH.

7. Actions of BradykininHypotensive Bradykinin is a vasoactive nonapeptide produced by the kinin system. It has a number of tissue actions: Vasodilation, possibly by a direct effect and via prostaglandin mediation Increase in vascular permeability by the opening of intercellular gaps in post-capillary venules Stimulation of phospholipase A2 and production of arachidonic acid Slow-onset, long-duration contraction of smooth muscle

8. Mechanism of Vasodilatory action of Kallikrein- kenin system