Which of the following is a powerful vasoconstrctor that increases the glomerular blood pressure and thereby the GFR?

Options

A. Renin
B. Angiotensin-II
C. Aldosterone
D. ANF

Answer

To determine which substance is a powerful vasoconstrictor that increases glomerular blood pressure and thereby the Glomerular Filtration Rate (GFR), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a powerful vasoconstrictor that increases glomerular blood pressure and GFR. We need to identify which of the given options fits this description.

2. **Identifying Key Terms**: The terms "vasoconstrictor," "glomerular blood pressure," and "GFR" are crucial. A vasoconstrictor narrows blood vessels, which can increase blood pressure.

3. **Analyzing the Options**:
- **Renin**: This is an enzyme that initiates the renin-angiotensin-aldosterone system (RAAS) but is not a vasoconstrictor itself.
- **Angiotensin II**: This is a peptide hormone that is a powerful vasoconstrictor. It increases blood pressure by constricting blood vessels and also stimulates aldosterone secretion, which helps to retain sodium and water, further increasing blood volume and pressure.
- **Aldosterone**: This hormone promotes sodium retention in the kidneys but does not directly act as a vasoconstrictor.
- **Atrial Natriuretic Factor (ANF)**: This hormone lowers blood pressure by promoting vasodilation and increasing sodium excretion, thus it is not a vasoconstrictor.

4. **Conclusion**: Among the options, **Angiotensin II** is the powerful vasoconstrictor that increases glomerular blood pressure and GFR. Therefore, the correct answer is **Angiotensin II**.

### Final Answer:
**Angiotensin II**

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