In urinary system, aldosterone takes part in retention (reabsorption) of

Options

A. `K^(+)`
B. `Na^(+)`
C. water
D. both b and c

Answer

To solve the question regarding the role of aldosterone in the urinary system, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Identify the Hormone**: Recognize that the hormone in question is aldosterone, which is classified as a mineralocorticoid. It is secreted by the adrenal cortex, specifically from the zona glomerulosa layer.

2. **Understand the Function of Aldosterone**: The primary function of aldosterone is to regulate sodium and potassium levels in the body. It promotes the reabsorption of sodium ions (Na+) in the kidneys.

3. **Mechanism of Action**: Aldosterone acts mainly on the distal convoluted tubule (DCT) and the collecting ducts of the nephron. It facilitates the reabsorption of sodium ions from the filtrate back into the bloodstream.

4. **Potassium Exchange**: While aldosterone promotes sodium reabsorption, it does so at the expense of potassium ions (K+), which are secreted into the filtrate. This means that as sodium is reabsorbed, potassium is excreted.

5. **Water Reabsorption**: The reabsorption of sodium ions leads to an increase in osmotic pressure, which in turn promotes the reabsorption of water. Thus, aldosterone indirectly contributes to water retention in the body.

6. **Conclusion**: Based on the functions of aldosterone, it is involved in the retention (reabsorption) of both sodium ions and water. Therefore, the correct answer to the question is option four: both sodium ions and water.

### Final Answer:
Aldosterone takes part in the retention (reabsorption) of sodium ions and water.

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