Antidiuretic hormone/vasopressin (ADH)
The main effect of antidiuretic hormone is to reduce urine output (diuresis is production of large volume of urine).
Antidiuretic hormone acts on kidneys to increase water retention, reduce urine volume and help to prevent dehydration and help to control fluid balance.
ADH act on distal convoluted and collecting duct of nephrons of kidney, increasing their permeability of water.
As result, reabsorption of water from glomerular filtrate is increased.
The tubule cells response by reabsorbing more water from forming urine and returning it to blood stream.
As a result, less urine is produce and blood volume increases.
The amount of ADH secreted in determined by osmotic pressure of blood circulating to osmoreceptors in hypothalamus.
Osmotic pressure rises, for an example as result of dehydration, secretion of ADH increases.
More water is reabsorbed and urine output is reduced.
When osmotic pressure of blood is low, for example after a large I fluid intake, secretion of ADH is reduced, less water reabsorbed and more urine is produced.
ADH is also called Vasopressin because it causes vasoconstriction at higher concentration.
Under certain condition, such as severe blood loss, large amount of ADH are released, causing rise in blood pressure.
Antidiuretic drug are used to manage some cases of hypertension and edema (water retention in tissue) , typical of congestive heart failure.
Drinking alcoholic beverages inhibits ADH secretion and causes large urine output (as result dry mouth).
ADH release is also inhibited by drinking excessive amount of water.
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