Which one is mainly responsible for absorption of `Na^(+)` in the PCT part of nephron?

Options

A. Angiotensin-II
B. Angiotensin-I
C. Aldosterone
D. Atrial Natriuretic Factor (ANF)

Answer

**Step-by-Step Solution:**

1. **Understanding the Nephron Structure**: The nephron is the functional unit of the kidney, consisting of several parts including the Bowman capsule, proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), and collecting duct.

2. **Identifying the Role of the Proximal Convoluted Tubule (PCT)**: The PCT is primarily responsible for the reabsorption of various substances, including sodium ions (Na+), from the filtrate back into the bloodstream.

3. **Recognizing the Hormonal Regulation**: The absorption of sodium in the PCT is regulated by hormones. The main hormone responsible for this process is aldosterone, which is a mineralocorticoid produced by the adrenal cortex.

4. **Locating Aldosterone Production**: Aldosterone is produced in the zona glomerulosa of the adrenal cortex, which is the outer layer of the adrenal glands located on top of the kidneys.

5. **Understanding Aldosterone's Function**: Aldosterone promotes sodium conservation in the kidneys, which means it enhances the reabsorption of sodium ions in the PCT, thus playing a crucial role in maintaining sodium balance in the body.

6. **Differentiating Other Hormones**: Other hormones such as atrial natriuretic factor (ANF) and angiotensin are involved in sodium regulation but have different roles. ANF promotes sodium excretion, while angiotensin II is a vasoconstrictor that influences blood pressure but does not directly promote sodium absorption in the PCT.

**Final Answer**: Aldosterone is mainly responsible for the absorption of Na+ in the proximal convoluted tubule (PCT) of the nephron.

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