Vasopressin, also known as antidiuretic hormone, is secreted by the posterior pituitary. The hypothalamus in the brain regulates the secretion of vasopressin. Neurons in the hypothalamus are sensitive to changes in sodium concentration in the blood and to low blood volume. Certain hormones, like angiotensin II can also stimulate vasopressin secretion. Vasopressin is transported in the blood to its primary target organ, the kidney. It stimulates the cells in the collecting ducts of the kidneys to reabsorb water from the urine. This causes a decrease in urine output and a rise in blood volume and consequently blood pressure. Vasopressin has many other physiological functions, including stimulating vasoconstriction, regulating cortisol secretion and regulating body temperature. Reports in medical literature have demonstrated that vasopressin also acts as a chemical messenger in the brain and controls multiple processes, including memory, sleep, behavior and thought.
Water Homeostasis
The primary function of vasopressin is maintain water homeostasis in the body. Vasopressin increases water reabsorption in the kidney and thereby increases blood volume and decreases urine output. Vasopressin stimulates proteins called aquaporins to form a water channel in the collecting ducts of kidneys. Vasopressin in concert with aldosterone and angiotensin II increases blood volume in response to hypovolemia, a serious medical condition caused by dehydration, bleeding, severe burns or diuretic drugs.
Vasoconstriction
The hormone vasopressin received its name from its effects on blood vessels. Vasopressin stimulates smooth muscle contraction causing vasoconstriction in the peripheral blood vessels. Unlike other vasoconstrictors, vasopressin paradoxically increases the dilation of pulmonary and coronary vessels. The dose and specific receptors on blood vessels determine whether vasopressin constricts or dilates a particular vascular bed. Because of vasopressin's selective vasoconstrictive effects, it has been used as a secondary treatment for vasodilatory shock. Vasodilatory shock is a medical emergency most commonly caused by sepsis and cardiovascular surgery. A clinical trial study published in the May 2003 issue of Circulation reported that treatment with vasopressin in combination with norepinephrine improved the cardiac outcomes of patients that had vasodilatory shock.
Heart
In addition to having effects on coronary vasculature, vasopressin increases heart contraction at low doses. However, the studies that have evaluated the effects of vasopressin on the heart conflict.
Adrenal Gland
Vasopressin stimulates the release of adrenocorticotropin hormone from the anterior pituitary. This hormone stimulates the adrenal gland to release cortisol.
Temperature Regulation
In the October 2003 issue of the Journal of Neuroscience Nursing, the authors report that vasopressin release during fever is beneficial in regulating body temperature.
Central Nervous System
Vasopressin also acts as a chemical messenger in the brain and was found to play a role in animals or humans in complex behavioral and cognitive functions, circadian rhythm and sexual behavior. Additional studies demonstrate a correlation between an elevation in vasopressin levels and anxiety, depression and schizophrenia. A report in a 2005 issue of Current Pharmaceutical Design states that drugs that target the actions of vasopressin may prove beneficial in the treatment of mood, anxiety and cognitive disorders. A human study published in the May 2006 issue of the Proceedings of the National Academy of Sciences discovered vasopressin affects social communication in both men and women. Despite the numerous central nervous system effects attributed to vasopressin in the scientific literature, clinical evidence of the therapeutic benefits of vasopressin or drugs that modulate vasopressin actions is lacking.
References
- Cardiovascular Physiology Concepts: Vasopressin (Antidiuretic Hormone)
- Critical Care: Science Review: Vasopressin and the Cardiovascular System
- Circulation: Arginine Vasopressin in Advanced Vasodilatory Shock: A Prospective, Randomized, Controlled Study
- Journal of Neuroscience Nursing: The Role of Arginine Vasopressin in Thermoregulation During Fever
- Current Pharmaceutical Design: The Central Vasopressinergic System: Examining the Opportunities for Psychiatric Drug Development
