The fluid coming out of proximal convoluted tubule has a concentration of about

Options

A. 200 mosmol/liter
B. 300 mosmol/liter
C. 600 mosmol/liter
D. 1200 mosmol/liter

Answer

To solve the question regarding the concentration of fluid coming out of the proximal convoluted tubule (PCT), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Proximal Convoluted Tubule Function**:
- The proximal convoluted tubule is a part of the nephron in the kidney where significant reabsorption of water and solutes occurs.

2. **Identifying Key Reabsorptions**:
- In the PCT, approximately 65% of water, sodium, potassium, and chloride ions are reabsorbed.
- Additionally, 100% of glucose and amino acids are reabsorbed.

3. **Analyzing the Concentration of Fluid**:
- Due to the high reabsorption rates of solutes and water, the concentration of the fluid that exits the PCT is affected.
- The fluid that comes out of the PCT is more concentrated than the original filtrate because a large volume of water is reabsorbed.

4. **Comparing Concentration Options**:
- The options given are:
- A) 200 mmol/L
- B) 300 mmol/L
- C) 600 mmol/L
- D) 1200 mmol/L
- Given that a significant amount of solutes is reabsorbed, the concentration of the fluid leaving the PCT is expected to be lower than the concentration of urine formed later in the nephron.

5. **Conclusion**:
- Based on the reabsorption rates and the typical concentration of fluid exiting the PCT, the concentration is approximately 300 mmol/L.
- Therefore, the correct answer is **B) 300 mmol/L**.