The function of renin is

Options

A. stimulation of corpus luteum
B. vasodilation
C. to reduce blood pressure
D. conversion of angiotensinogen to angiotensin-l

Explanation

### Step-by-Step Solution:

1. **Understand the Source of Renin**: Renin is an enzyme secreted primarily by the juxtaglomerular apparatus in the kidneys. This is a specialized structure that plays a crucial role in regulating blood pressure and fluid balance.

2. **Identify the Trigger for Renin Release**: Renin is released in response to a decrease in blood volume or blood pressure. When the blood pressure drops, the juxtaglomerular apparatus detects this change and releases renin into the bloodstream.

3. **Function of Renin**: The primary function of renin is to initiate the renin-angiotensin-aldosterone system (RAAS). Renin catalyzes the conversion of angiotensinogen, an inactive protein produced by the liver, into angiotensin I.

4. **Conversion of Angiotensinogen**: Angiotensin I is then converted to angiotensin II by the action of the enzyme angiotensin-converting enzyme (ACE), primarily in the lungs.

5. **Effects of Angiotensin II**: Angiotensin II has several important functions:
- It stimulates the adrenal cortex to release aldosterone, which increases sodium reabsorption in the kidneys, leading to increased blood volume and blood pressure.
- It causes vasoconstriction, which also contributes to an increase in blood pressure.

6. **Evaluate the Options**:
- **Option A**: Stimulation of corpus luteum - Incorrect, as this is related to reproductive hormones.
- **Option B**: Vasodilation - Incorrect, as renin leads to vasoconstriction.
- **Option C**: To reduce blood pressure - Incorrect, as renin actually increases blood pressure.
- **Option D**: Conversion of angiotensinogen to angiotensin I - Correct, as this is the primary function of renin.

7. **Conclusion**: The correct answer to the question about the function of renin is **Option D: Conversion of angiotensinogen to angiotensin I**.