Vasopressin is a key hormone in the human system that plays a major role in maintaining blood pressure, kidney health, as well as fluid and electrolyte balance in the body. Also termed as Antidiuretic Hormone (ADH), vasopressin is synthesized by specialized nerve cells located in the hypothalamus at the base of the brain. After production in the hypothalamus, vasopressin is carried by nerve fibres i.e. axons down to the posterior pituitary gland, from where it is introduced into blood circulation.
The secretion and delivery into bloodstream of vasopressin is primarily operated by the pituitary gland, which facilitates the release of the hormone based on various factors. In times of reduced blood volume due to haemorrhage, or low blood pressure, sensors in the heart known as baroreceptors induce the production of ADH. Owing to dehydration, when salt concentrations in the body increase, the synthesis and release of vasopressin is supported, based on the activity of sensors in the brain called osmoreceptors. Furthermore, when the body is undergoing stress, or facing thirst, nausea, vomiting, the production and release of vasopressin occurs, wherein the hormone plays a protective role by elevating fluid volumes in the body and preventing harmful effects such as tissue injury and severe dehydration.
Vasopressin And Its Structure:
The antidiuretic property of vasopressin was discovered a century ago in 1913, by reputed Italian scientist F. Farini in Venice and well-known German researcher von den Velden in Dusseldorf, who worked independently on investigating hormonal actions in the human system. Diuretics refers to compounds that promote the elimination of excess salts and water from the body, while antidiuretics have the opposite effect – retention of water and salts in the body to prevent dehydration and electrolyte imbalance. Following this, in 1927 - 1928, renowned American chemist Oliver Kamm successfully isolated and purified both oxytocin and vasopressin from bovine pituitary extracts. During the period from 1951 to 1953. Vincent du Vigneaud, an established American biochemist, successfully determined the structure of arginine vasopressin (AVP) to be a sequence of nine amino acids. He also was the first researcher to chemically synthesize vasopressin in the laboratory in 1954. For his pioneering work on delineating the hormonal structure and function of both polypeptides - oxytocin and vasopressin, Vincent du Vigneaud was awarded the prestigious Nobel Prize In Chemistry in the year 1955.
Vasopressin is a polypeptide hormone, with the structure of arginine vasopressin being a sequence of nine amino acids i.e. a nonapeptide - Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2. The chemical structure of vasopressin is similar to that of oxytocin, also a peptide hormone secreted by the pituitary gland.
Functions Of Vasopressin:
Vasopressin is involved in several vital functions in the human body, including:
- Retaining water, salts i.e. sodium in the body in times of stress, injury, dehydration, owing to its antidiuretic property
- Regulating the release of urine from the kidneys
- Controlling blood pressure and preserving optimal blood volume, by influencing the activity of the kidneys and blood vessels
- Maintaining normal internal body temperature within the system, in the region surrounding cells and tissues
- Sustains the body’s circadian rhythm and regulates the periods of sleep and wakefulness in a 24-hour cycle
Adverse Effects Of Hormonal Imbalance In Vasopressin:
When levels of vasopressin in the body are lower than normal, it triggers the kidneys to excrete vast volumes of water. When the amount of urine eliminated increases, it invariably results in dehydration and a drop in blood pressure.
Low levels of vasopressin are chiefly caused by hampered structural form and functioning of the hypothalamus segment within the brain and pituitary gland. Other factors that prompt the decreased secretion of vasopressin/antidiuretic hormone comprise primary polydipsia – a condition involving excessive and compulsive drinking of water, besides diabetes insipidus – wherein tumours/inflammation in the hypothalamus lead to reduced production of vasopressin or the kidneys are not sensitive to the polypeptide hormone to carry out normal bodily reactions. Diabetes insipidus leads to incessant thirst and surplus discharge of urine triggering intense dehydration if left untreated.
When vasopressin levels in the body are very high, it gives rise to increased water retention by the kidneys. It also induces another health anomaly known as Syndrome Of Inappropriate Anti-Diuretic Hormone Secretion (SIADH), which is a type of hyponatremia wherein the body’s salt/sodium concentrations are rather low. This happens due to massive water retention which dilutes the blood and lowers salt levels in circulation. The major factors that prompt high levels of antidiuretic hormone in the system are lung ailments such as lung cancer, tumours/inflammation of the hypothalamus or pituitary gland or even side-effects of certain potent medications.