Which of the following is NOT listed as a major pathway contributing to essential hypertension?

• A. Increased sympathetic activity leading to vasoconstriction, tachycardia, and renin release.
• B. Activation of the renin–angiotensin–aldosterone system causing Ang II–mediated vasoconstriction and aldosterone-driven volume expansion.
• C. Decreased endothelin production leading to lower vascular tone.
• D. Renal sodium handling abnormalities promoting extracellular fluid volume expansion.

Answer: (C)

Essential hypertension arises from multiple mechanisms that increase vascular resistance and expand extracellular fluid volume. Increased sympathetic activity raises vasoconstriction, speeds heart rate, and boosts renin release, all of which push blood pressure higher. Activation of the renin–angiotensin–aldosterone system (Ang II–mediated vasoconstriction and aldosterone-driven sodium and water reabsorption) also drives hypertension by both constricting vessels and expanding circulating volume. Renal handling of sodium is another major factor: abnormal sodium reabsorption promotes extracellular fluid volume expansion, raising blood pressure.

Endothelin-1, produced by endothelial cells, is a potent vasoconstrictor; in essential hypertension, endothelin signaling is typically upregulated, contributing to higher vascular tone. A statement describing decreased endothelin production leading to lower vascular tone would actually tend to lower blood pressure, not raise it, so it does not represent a major pathway driving essential hypertension.