Endothelium derived relaxing factor (EDRF) induced vasodilatation is mediated by:
**Core Concept**
EDRF (Endothelium-derived relaxing factor) is a crucial signaling molecule produced by the endothelium that causes vasodilation, leading to decreased blood pressure and increased blood flow. EDRF is released in response to various stimuli, including shear stress, and plays a vital role in maintaining vascular tone.
**Why the Correct Answer is Right**
EDRF is primarily mediated by nitric oxide (NO), a potent vasodilator that activates guanylate cyclase in smooth muscle cells, leading to an increase in cyclic guanosine monophosphate (cGMP) levels. This results in the relaxation of smooth muscle cells, causing vasodilation. The endothelium produces NO through the action of endothelial nitric oxide synthase (eNOS) enzyme.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because prostaglandins, such as prostacyclin (PGI2), are also produced by the endothelium and cause vasodilation, but they are not the primary mediator of EDRF.
**Option B:** This option is incorrect because endothelin-1 (ET-1) is a potent vasoconstrictor produced by the endothelium, which has the opposite effect of EDRF.
**Option C:** This option is incorrect because bradykinin is a vasodilator, but it is not the primary mediator of EDRF.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the endothelium plays a crucial role in maintaining vascular tone, and dysfunction of the endothelium is associated with various cardiovascular diseases, including hypertension and atherosclerosis.
**Correct Answer: A. Nitric oxide**