Vasopressin, also called antidiuretic hormone (A D H) or arginine vasopressin
(AVP), is another hormone key to water homeostasis and blood pressure
regulation. A rginine vasopressin is produced in the neurones of the
hypothalamus and stored in vesicles within the posterior pituitary.
Vasopressin is released in response to increased blood osmolality detected
by hypothalamic osmoreceptors; systemic hypotension or hypovolaemia
detected by cardiopulmonary baroreceptors of the great veins and atria; or
angiotensin I I acting on the hypothalamus.
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Vasopressin is a peptide hormone secreted by the hypothalamus via the
posterior pituitary. Its primary role is the regulation of body fluid balance. It
is secreted in response to hypotension and promotes retention of water by
action on specific cAMP-coupled V2 receptors. It causes vasoconstriction by
stimulating V1 receptors in VSM and is particularly potent in hypotensive
patients. It is increasingly used in the treatment of refractory vasodilatory
shock which is resistant to catecholamines. The vasopressin analogue
desmopressin is used to treat diabetes insipidus and in the management of
von Willebrand's disease. Terlipressin (another analogue) is used to limit
bleeding from oesophageal varices in patients with portal hypertension.
When used for the management of low SVR states, vasopressin is
administered as an i.v. infusion at a rate of 0.01–0.1 units min–1.
Biological Functions
Human vasopressin, or Arg-vasopressin, is chemically very similar to oxytocin and therefore
sometimes is referred to as [Phe3, Arg8]oxytocin. The physiological role of
vasopressin is the regulation of water reabsorption in the renal tubules (an antidiuretic action,
thus often referred to as the antidiuretic hormone). In high doses, vasopressin promotes the
contraction of arterioles and capillaries, resulting in an increase in blood pressure, thus the
name vasopressin. An inadequate output of pituitary antidiuretic hormone can cause diabetes
insipidus, which is characterized by the chronic excretion of large amounts of pale urine and
results in dehydration and extreme thirst.
Clinical Use
The nonapeptide vasopressin is well known for its role on fluid metabolism, but it also is a
key regulator of the HPA axis. Stress stimulates the release of vasopressin in the pituitary gland, where it
strongly potentiates the effects of CRF on adrenocorticotropic hormone release. These findings suggest that HPA axis dysregulation in depression might be associated with
the development of centrally acting vasopressin receptor antagonists for the treatment of depression.
