Which of the following is not secreted by the kidney?

Options

A. Renin
B. Angiotensin I
C. Erythropoietin
D. 1, 25 Dihydroxycholecalecalciferol

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which substance is not secreted by the kidney among the given options: renin, angiotensin, erythropoietin, and 1,2,5-dihydroxycholecalciferol.

2. **Identifying the Functions of Each Substance**:
- **Renin**: This enzyme is secreted by the juxtaglomerular cells of the kidney and plays a crucial role in the regulation of blood pressure.
- **Angiotensin**: Specifically, angiotensinogen (the precursor to angiotensin I) is produced by the liver. Angiotensin I is then converted to angiotensin II, which is involved in blood pressure regulation. Therefore, angiotensin itself is not secreted by the kidney.
- **Erythropoietin**: This hormone is produced and secreted by the kidneys and is responsible for stimulating red blood cell production in the bone marrow.
- **1,2,5-Dihydroxycholecalciferol**: This is the active form of vitamin D, which is also produced in the kidneys and is important for calcium metabolism.

3. **Conclusion**: Based on the functions and origins of these substances, the one that is not secreted by the kidney is **angiotensinogen** (which is produced by the liver).

4. **Final Answer**: Angiotensinogen is not secreted by the kidney.

---