In the renal tubules the permeabillity of the distal convoluted tubule and collecting duct to water is controlled by

Options

A. renin
B. calcitonin
C. vasopressin
D. growth hormone

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the control of water permeability in the distal convoluted tubule and collecting duct of the renal tubules.

2. **Identifying the Relevant Hormones**: The permeability of these structures to water is primarily influenced by hormones. The key hormones involved in regulating water reabsorption in the kidneys are Antidiuretic Hormone (ADH), also known as vasopressin, and aldosterone.

3. **Focusing on Antidiuretic Hormone (ADH)**: Among these hormones, ADH plays a crucial role in increasing the permeability of the distal convoluted tubule and collecting duct to water. When ADH is present, it promotes the insertion of aquaporin channels in the membranes of these tubules, allowing more water to be reabsorbed back into the bloodstream.

4. **Conclusion**: Therefore, the hormone that controls the permeability of the distal convoluted tubule and collecting duct to water is **Antidiuretic Hormone (ADH)**.

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