Increased permeability in acute inflammation is due to?
**Core Concept**
Increased permeability in acute inflammation is a critical step in the inflammatory response, allowing the migration of white blood cells (leukocytes) from the bloodstream into the affected tissue. This process is mediated by the release of chemical mediators and the activation of endothelial cells, leading to changes in the vascular permeability.
**Why the Correct Answer is Right**
The correct answer involves the release of histamine from mast cells and platelets, which binds to H1 receptors on endothelial cells, causing vasodilation and increasing vascular permeability. This leads to the leakage of fluid, proteins, and white blood cells into the interstitial space, resulting in edema and tissue damage. The endothelial cells also express adhesion molecules, which facilitate the adhesion and transmigration of leukocytes across the endothelial layer.
**Why Each Wrong Option is Incorrect**
* **Option A:** Vasopressin is a vasoconstrictor that would decrease vascular permeability, not increase it.
* **Option B:** Bradykinin is a vasodilator and increases vascular permeability, but it is not the primary mediator of increased permeability in acute inflammation.
* **Option D:** Catecholamines, such as adrenaline, can increase heart rate and blood pressure, but they do not directly increase vascular permeability in acute inflammation.
**Clinical Pearl / High-Yield Fact**
Remember the "5 Ps" of acute inflammation: pain, redness, swelling, heat, and loss of function. Increased vascular permeability is a key component of the inflammatory response, leading to swelling and tissue damage.
**Correct Answer: C. Histamine. Histamine.**