ADH PHYSIOLOGIC FUNCTIONHARITH RIYADH AKAKI TSERETELI STATE UNIVERSITY

ADH • Antidiuretic hormone, also known commonly as arginine

vasopressin, is a nine amino acid peptide secreted from the posterior pituitary. Within hypothalamic neurons, the hormone is packaged in secretory vesicles with a carrier protein called neurophysin, and both are released upon hormone secretion

Physiologic Effects of Antidiuretic • Hormone Effects on the Kidney The single most important effect of antidiuretic hormone is to conserve body water by reducing the loss of water in urine. A diuretic is an agent that increases the rate of urine formation. Injection of small amounts of antidiuretic hormone into a person or animal results in antidiuresis or decreased formation of urine, and the hormone was named for this effect

• Antidiuretic hormone binds to receptors on cells in the collecting ducts of the kidney and promotes reabsorption of water back into the circulation. In the absense of antidiuretic hormone, the collecting ducts are virtually impermiable to water, and it flows out as urine.

• Antidiuretic hormone stimulates water reabsorbtion by stimulating insertion of "water channels" or aquaporins into the membranes of kidney tubules. These channels transport solute-free water through tubular cells and back into blood, leading to a decrease in plasma osmolarity and an increase osmolarity of urine

• The more concentrated the plasma, the more ADH is released into the blood. When the ADH reaches the kidneys, it causes them to reabsorb more water. This keeps more water in the body and produces more concentrated urine .When the plasma is more dilute, less ADH is released into the bloodstream. This allows more water to leave the kidneys, producing more dilute urine.This method of control is an example of negative feedback

Effects on the Vascular System• In many species, high concentrations of antidiuretic

hormone cause widespread constriction of arterioles, which leads to increased arterial pressure. It was for this effect that the name vasopressin was coined. In healthy humans, antidiuretic hormone has minimal pressor effects

How alcohol and ecstasy affect ADH• Alcohol suppresses ADH production. This causes the

kidneys to produce more dilute urine. It can lead to dehydration. Ecstasy increases ADH production. This causes the kidneys to reabsorb water. It can result in the body having too much water

Disease• States The most common disease of man and animals

related to antidiuretic hormone is diabetes insipidus. This condition can arise from either of two situations:

• Hypothalamic ("central") diabetes insipidus results from a deficiency in secretion of antidiuretic hormone from the posterior pituitary. Causes of this disease include head trauma, and infections or tumors involving the hypothalamus.

• Nephrogenic diabetes insipidus occurs when the kidney is unable to respond to antidiuretic hormone. Most commonly, this results from some type of renal disease, but mutations in the ADH receptor gene or in the gene encoding aquaporin-2 have also been demonstrated in affected humans