Which of the following activates the adrenal cortex to release aldosterone ?

Options

A. Renin
B. Angiotensin-I
C. Angiotensin-II
D. Angiotensinogen

Answer

To solve the question "Which of the following activates the adrenal cortex to release aldosterone?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Aldosterone**: Aldosterone is a hormone produced by the adrenal cortex that helps regulate blood pressure and electrolyte balance by promoting sodium retention and potassium excretion in the kidneys.

2. **Identify the Stimuli for Aldosterone Release**: The release of aldosterone is primarily stimulated by the renin-angiotensin-aldosterone system (RAAS).

3. **Recognize the Components of RAAS**:
- **Renin**: An enzyme secreted by the kidneys in response to low blood pressure or low sodium levels.
- **Angiotensinogen**: A protein produced by the liver that is converted into angiotensin I by renin.
- **Angiotensin I**: An inactive precursor that is converted into angiotensin II by the action of angiotensin-converting enzyme (ACE) primarily in the lungs.

4. **Identify the Active Form**: Angiotensin II is the active form that directly stimulates the adrenal cortex to release aldosterone.

5. **Evaluate the Options**:
- **Option A: Renin** - It initiates the process but does not directly stimulate aldosterone release.
- **Option B: Angiotensin I** - It is the precursor and not the active form that stimulates aldosterone release.
- **Option C: Angiotensin II** - This is the correct answer as it activates the adrenal cortex to release aldosterone.
- **Option D: Angiotensinogen** - It is the substrate for renin but does not have a direct role in stimulating aldosterone release.

6. **Conclusion**: Based on the above analysis, the correct answer is **Option C: Angiotensin II**.