Which hormone is responsible for increasing water permeability in the distal tubule?

The hormone responsible for increasing water permeability in the distal tubule is antidiuretic hormone (ADH), also known as vasopressin. ADH is produced in the hypothalamus and released by the posterior pituitary gland in response to high plasma osmolality or low blood volume. When secreted, ADH binds to its receptors in the cells of the distal convoluted tubule and collecting ducts of the kidneys. This binding promotes the insertion of water channels called aquaporins into the cell membranes, which increases the permeability of these segments of the nephron to water.

As a result, more water is reabsorbed from the tubular fluid back into the bloodstream, concentrating the urine and maintaining hydration and electrolyte balance. This process is essential for regulating blood pressure and fluid balance in the body. The increase in water reabsorption helps prevent dehydration by conserving water when it is needed, making ADH a critical hormone in the management of bodily fluids.