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

Step 1: Background on bradykinin.
Bradykinin is a kinin generated by the kallikrein-kinin system during inflammation. It is a key vasoactive peptide.

Step 2: Part (a), the exception among its actions.
Bradykinin causes vasodilatation, increases vascular permeability, and produces pain. However it causes bronchoconstriction, not bronchodilatation. So in part (a) the false statement is bronchodilatation.

Step 3: Part (b), the most important role in acute inflammation.
In acute inflammation, the hallmark vascular change is increased vascular permeability that lets protein-rich fluid leak out and form exudate. Bradykinin is one of the principal mediators of this increased vascular permeability, and that is its most important role here. This matches option A.

Step 4: Why not the others for part (b).
Vasodilatation is shared by many mediators (histamine, prostaglandins, nitric oxide), so it is not the defining bradykinin role. Pain is an action of bradykinin but is not its key inflammatory function. Bronchoconstriction is not a feature of acute inflammation as asked.

Step 5: Conclusion.
The most important role of bradykinin in acute inflammation is increased vascular permeability, option A. (For part a, the action it does NOT have is bronchodilatation, since bradykinin causes bronchoconstriction.)