Reabsorption of which of the following substances in the collecting ducts is enhanced by aldosterone :

Options

A. `K^(+) `
B. `Ca^+`
C. `Na^(+) `
D. `Cl^(-)`

Explanation

To solve the question regarding which substance's reabsorption in the collecting ducts is enhanced by aldosterone, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Aldosterone**: Aldosterone is a hormone produced by the adrenal glands. Its primary function is to regulate sodium and potassium levels in the body.

2. **Identify the Target Area**: Aldosterone acts mainly on the distal convoluted tubule (DCT) and the collecting ducts of the nephron in the kidneys.

3. **Determine the Substances Involved**: The question lists four substances: potassium, calcium, sodium, and chloride ions. We need to identify which of these is reabsorbed more due to the action of aldosterone.

4. **Focus on Sodium Reabsorption**: Aldosterone specifically enhances the reabsorption of sodium ions (Na+) in the collecting ducts. This is crucial for maintaining blood pressure and fluid balance in the body.

5. **Consider the Effect on Other Ions**: While aldosterone promotes sodium reabsorption, it also has an effect on potassium. It causes potassium ions (K+) to be excreted in exchange for sodium reabsorption, but the primary enhancement of reabsorption by aldosterone is for sodium.

6. **Conclusion**: Based on the above points, the correct answer to the question is sodium ions.

### Final Answer:
The reabsorption of sodium ions in the collecting ducts is enhanced by aldosterone.

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