Which option describes a major action of chemical mediators in inflammation?

• A. Local vasodilation leading to hyperemia and increased permeability with plasma protein leakage
• B. Immediate tissue necrosis
• C. Inhibition of leukocyte migration
• D. Decrease vascular permeability

Answer: (A)

Chemical mediators drive the early vascular changes of inflammation, especially causing local vasodilation and increased vascular permeability. This vasodilation raises blood flow to the area (hyperemia), producing redness and warmth, while the increased permeability allows plasma proteins to leak into the tissue, leading to edema and providing proteins and cells to fight the insult. Histamine, bradykinin, and nitric oxide are classic mediators that promote these changes.

Immediate tissue necrosis is not a primary action of inflammatory mediators; they regulate the process, not cause rapid cell death. Inhibition of leukocyte migration would dampen the inflammatory response, whereas many mediators actually promote leukocyte recruitment. Decreasing vascular permeability runs counter to the main inflammatory sequence, which involves increasing permeability to enable exudation and defense at the site.