Which of the following is inactivated in the lung?
**Core Concept**
The question is testing the student's knowledge of the inactivation process of certain substances in the body, specifically in the lung. The correct answer involves a specific enzyme or system that is responsible for inactivating a particular compound.
**Why the Correct Answer is Right**
The correct answer is Angiotensin-Converting Enzyme (ACE). ACE is a carboxypeptidase that is primarily found in the lung, where it plays a crucial role in the renin-angiotensin-aldosterone system (RAAS). ACE is responsible for converting angiotensin I to angiotensin II, a potent vasoconstrictor that increases blood pressure. However, ACE also inactivates bradykinin, a vasodilator that helps to counteract the effects of angiotensin II. The inactivation of bradykinin by ACE is a key mechanism by which ACE contributes to the development of hypertension.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the inactivation process in the lung.
**Option B:** This option is not a correct answer, as the inactivation process in the lung is not related to this substance.
**Option C:** This option is not a correct answer, as the inactivation process in the lung is not related to this enzyme.
**Clinical Pearl / High-Yield Fact**
ACE inhibitors, which block the action of ACE, are commonly used to treat hypertension and heart failure. They work by increasing bradykinin levels, leading to vasodilation and decreased blood pressure.
**Correct Answer:** C. Angiotensin-Converting Enzyme (ACE)