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How does vasopressin regulate water loss through the kidneys?
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Endocrine system
The glands of the human endocrine system.
Vasopressin, also known as antidiuretic hormone (ADH), regulates water balance by controlling the permeability of the kidneys to water.12
When the body needs to conserve water—detected by osmoreceptors in the hypothalamus or baroreceptors sensitive to blood volume—the pituitary gland releases vasopressin into the bloodstream.12
In the kidneys, vasopressin acts on the cells of the collecting ducts:
- Aquaporin Activation: Vasopressin triggers the fusion of vesicles containing aquaporins (water channels) with the cell membrane.1
- Water Reabsorption: These channels allow water to move out of the collecting ducts and back into the circulation, effectively concentrating the urine.12
- Inhibition: Conversely, when blood volume is high or plasma osmolality is low, vasopressin secretion decreases. This makes the collecting ducts impermeable to water, leading to the excretion of larger volumes of dilute urine.12
This feedback mechanism is essential for maintaining stable osmolality and protecting cellular function.1