Question

(a) Actions of bradykinin include all of the following, except: Vasodilatation, Bronchodilatation, Increased vascular permeability, Pain. (b) What is the most important role of bradykinin in acute inflammation? The options below answer part (b).

• A. Increase in vascular permeability
• B. Vasodilatation
• C. Mediation of pain
• D. Bronchoconstriction

Hint:

Bradykinin constricts bronchi, and its inflammatory hallmark is leaky vessels.

Answer 1

The Correct Option is A

This double question tests both what bradykinin does and which of its actions matters most in inflammation.

Take the list of its effects first. Bradykinin is a powerful vasodilator, it widens the gaps between endothelial cells to raise vascular permeability, and it directly stimulates nerve endings to cause pain. On the airways, though, it does the opposite of relaxation: it constricts bronchial smooth muscle. So any statement crediting it with bronchodilatation is the odd one out, since the true effect is bronchoconstriction.

Now for the role that counts most in acute inflammation. The defining event of the acute response at the microvasculature is leakage of plasma proteins through a more permeable wall, producing exudate and tissue swelling. Bradykinin is a major driver of this permeability change, and that is the action highlighted as its chief contribution.

The alternatives fall short. Vasodilatation is produced by a long list of mediators, so it is not uniquely bradykinin. Pain is real but secondary to the vascular role. Bronchoconstriction is not what acute inflammation is about. Hence the headline answer is increased vascular permeability.
\[\boxed{\text{Increase in vascular permeability (option A)}}\]