Arginine vasopressin receptor

The Arginine Vasopressin Receptor (AVPR) is a class of G protein-coupled receptors (GPCRs) that bind to the hormone arginine vasopressin (AVP). These receptors play a crucial role in the regulation of water balance, blood pressure, and social behavior in humans and other mammals.

Types of Arginine Vasopressin Receptors

There are three main types of arginine vasopressin receptors, each with distinct functions and tissue distributions:

V1A Receptor

The V1A receptor is primarily found in vascular smooth muscle cells, where it mediates vasoconstriction and increases blood pressure. It is also present in the liver, platelets, and certain areas of the brain. The V1A receptor is coupled to the Gq protein, which activates the phospholipase C pathway, leading to an increase in intracellular calcium levels.

V1B Receptor

The V1B receptor, also known as the V3 receptor, is predominantly located in the anterior pituitary gland. It plays a role in the release of adrenocorticotropic hormone (ACTH) in response to stress. The V1B receptor is also coupled to the Gq protein and activates similar intracellular signaling pathways as the V1A receptor.

V2 Receptor

The V2 receptor is primarily expressed in the renal collecting ducts of the kidney. It is responsible for the antidiuretic effects of vasopressin, promoting water reabsorption and concentrating urine. The V2 receptor is coupled to the Gs protein, which activates adenylate cyclase and increases intracellular cyclic AMP (cAMP) levels.

Physiological Roles

Arginine vasopressin receptors are involved in several key physiological processes:

Regulation of Water Balance

The V2 receptor in the kidney is crucial for maintaining water balance. When plasma osmolality increases, vasopressin is released from the posterior pituitary gland, binds to V2 receptors, and promotes water reabsorption in the collecting ducts, thus reducing urine output and conserving water.

Blood Pressure Regulation

The V1A receptor mediates vasoconstriction, which increases peripheral resistance and raises blood pressure. This is particularly important during hypovolemic shock or hemorrhage, where vasopressin helps maintain blood pressure.

Social and Behavioral Effects

Vasopressin receptors, particularly V1A, are implicated in social behaviors, including pair bonding, aggression, and social recognition. These effects are mediated through receptor expression in specific brain regions.

Clinical Significance

Diabetes Insipidus

Mutations in the V2 receptor can lead to nephrogenic diabetes insipidus, a condition characterized by the inability to concentrate urine, resulting in excessive urination and thirst.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Overactivity of vasopressin receptors, particularly V2, can lead to SIADH, where excessive water retention causes hyponatremia.

Pharmacological Targeting

Vasopressin receptor antagonists, such as tolvaptan, are used to treat conditions like SIADH and heart failure by promoting water excretion without affecting electrolyte balance.

See Also

• Vasopressin
• G protein-coupled receptor
• Diabetes insipidus
• Hyponatremia

External Links

• [Link to relevant external resources]

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