What is the function of ADH (Vasopressin) in renal physiology?

The function of ADH, or antidiuretic hormone (vasopressin), in renal physiology is primarily related to the regulation of water reabsorption in the kidneys. ADH is secreted by the posterior pituitary gland and acts on the renal collecting ducts to increase their permeability to water.

When ADH binds to its receptors on the cells of the collecting ducts, it promotes the insertion of aquaporin channels into the cell membranes. These channels facilitate water's movement from the tubular fluid back into the bloodstream, effectively concentrating the urine and reducing water loss from the body. The primary physiological role of ADH is to help maintain body fluid homeostasis, particularly during states of dehydration or when plasma osmolality is high.

This mechanism is crucial for regulating blood volume and blood pressure, as increased water reabsorption by the kidneys directly affects these parameters. Therefore, the role of ADH in enhancing water reabsorption directly supports overall fluid balance in the body.