Bradykinin major action is to...

• A. Promotes platelet aggregation
• B. Inhibits immune cell recruitment to the site
• C. Activates pain receptors -> mast cells & basophils release histamine -> histamine & bradykinin cause capillary dilation
• D. Causes bronchoconstriction and mucus production

Answer: (C)

Bradykinin is a key mediator of inflammation that prominently produces pain and vascular changes. It directly activates sensory nociceptors, giving the characteristic burning pain of an inflammatory response. This activation also tends to promote the release of histamine from mast cells and basophils, and the combined action of histamine and bradykinin leads to capillary dilation and increased vascular permeability, causing edema. This sequence—pain receptor activation followed by mediator release and vasodilation—captures bradykinin’s major role in inflammation, making the option describing this pathway the best fit.

The other ideas don’t align as closely: platelet aggregation is driven by other mediators like thromboxane, not bradykinin; bradykinin does not inhibit immune cell recruitment (it actually promotes vascular permeability and cell influx); and bronchoconstriction with mucus production is more typical of histamine and leukotrienes in allergic-type responses, not the defining action of bradykinin.