Antidiuretic hormone (ADH), also known as vasopressin, plays a crucial role in regulating the body's water balance. Its primary effect on the kidneys is to decrease urination. Specifically, ADH increases water reabsorption in the kidneys by promoting the insertion of aquaporin-2 channels in the membranes of collecting duct cells. This action enhances the kidneys' ability to retain water, leading to a concentration of urine and a reduction in the volume of urine produced.
When ADH is released, it signals the kidneys to reabsorb more water back into the bloodstream during times of dehydration or high plasma osmolality. As a result, less water is excreted, which conserves body fluids and helps maintain blood volume and osmotic balance. This mechanism is particularly important in circumstances such as dehydration, where the body needs to retain as much water as possible to prevent significant fluid loss.
The other effects mentioned in the choices, such as increasing urination, reducing blood pressure, or stimulating glycogen breakdown, do not align with the primary role of ADH in kidney function. Instead, ADH's main physiological purpose is to decrease urine output by increasing water reabsorption, making it essential for fluid homeostasis in the