Increased vascular permeability in acute inflammation is due to ?
**Core Concept**
The increase in vascular permeability during acute inflammation is a critical step that allows the movement of white blood cells and proteins from the bloodstream into the affected tissue. This process is mediated by the release of various chemical mediators, including histamine, bradykinin, and leukotrienes, which act on specific receptors to alter the permeability of blood vessels. The resulting increase in vascular permeability enables the recruitment of immune cells to the site of inflammation.
**Why the Correct Answer is Right**
During acute inflammation, the release of histamine from mast cells and basophils triggers the contraction of endothelial cells and the opening of intercellular gaps, leading to increased vascular permeability. Histamine acts on H1 receptors on endothelial cells, causing the contraction of these cells and the release of nitric oxide, which further increases vascular permeability. Additionally, the release of bradykinin and leukotrienes also contributes to the increase in vascular permeability by stimulating the release of prostaglandins and other chemical mediators.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the primary mechanism of increased vascular permeability during acute inflammation.
**Option B:** This option is incorrect because it refers to a process that occurs during chronic inflammation, where the increased vascular permeability is sustained over a longer period.
**Option C:** This option is incorrect because it refers to a mechanism that is involved in the regulation of blood pressure, rather than the increase in vascular permeability during acute inflammation.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the increase in vascular permeability during acute inflammation is a critical step that enables the recruitment of white blood cells to the site of inflammation. This process is mediated by the release of histamine and other chemical mediators, which act on specific receptors to alter the permeability of blood vessels.
**Correct Answer: C. Histamine.**