VASOPRESSIN
It is also called as anti diuretic hormone (ADH).
STRUCTURE:-
It is a peptde having 9 amino acids. Different from oxytocin in just 2 amino acids. ADH has seven amino acids same as oxytocin and in addition to phenylalanine and argenine.
FUNCTIONS:-
STRUCTURE:-
It is a peptde having 9 amino acids. Different from oxytocin in just 2 amino acids. ADH has seven amino acids same as oxytocin and in addition to phenylalanine and argenine.
FUNCTIONS:-
- At higher concentrations ADH has potent effect i.e. it causes increased constrictions of blood throughout the body. Hence ADH is also called as vasopressin.This effect causes increase in mean arterial pressure.
- ADH as the name suggests prevents excessive loss of water through urine by increasing water reabsorption in the renal tubules.This occurs through insertion of water channels (Aquaporin-2) into the apical membrane of distal tubule and collecting duct epithelial cells. Aquaporins allow water to move down their osmotic gradient and out of the nephron, increasing the amount of water re-absorbed from the filtrate (forming urine) back into the bloodstream. Increasing permeability of the inner medullary portion of the collecting duct to urea by regulating the cell surface expression of urea transporters[4], which facilitates its reabsorption into the medullary interstitium as it travels down the concentration gradient created by removing water from the connecting tubule, cortical collecting duct, and outer medullary collecting duct.
- Vasopressin released within the brain has many actions:
- It has been implicated in memory formation, including delayed reflexes, image, short- and long-term memory, though the mechanism remains unknown; these findings are controversial. However, the synthetic vasopressin analoguedesmopressin has come to interest as a likely nootropic.
- Vasopressin is released into the brain in a circadian rhythm by neurons of the supraoptic nucleus.
- Vasopressin released from centrally projecting hypothalamic neurons is involved in aggression, blood pressure regulation and temperature regulation.
- Selective AVPr1a blockade in the ventral pallidum has been shown to prevent partner preference, suggesting that these receptors in this ventral forebrain region are crucial for pair bonding.
- Recent evidence suggests that vasopressin may have analgesic effects.The analgesia effects of vasopressin were found to be dependent on both stress and gender.
REGULATION:-
ADH levels are directly related to the solute concentration of blood. When encountered with highly osmotic fluid the osmo regulators loose fluid. They in turn send stimulus to the supra optic nucleus of the hypothalamus to release ADH.
When the solute concentration returns to normal the stimulus from osmo-regulators ceases and the ADH levels wane. Any factor that changes the solute concentration can influence ADH secretion.
Normal ResultsNormal values -- 0 - 4.7 pg/mL
Note: pg/mL = picograms per milliliter [21]
DISORDERS:-
Heart failure is associated with what might be viewed as a paradoxical increase in AVP. Increased blood volume and atrial pressure associated with heart failure suggest that AVP secretion might be inhibited, but it is not. It may be that sympathetic and renin-angiotensin system activation in heart failure override the volume and low pressure cardiovascular receptors (as well as the hypothalamic control of AVP release) and cause an increase in AVP secretion. Nevertheless, this increase in AVP during heart failure may contribute to the increase in systemic vascular resistance as well as the enhanced renal retention of fluid that accompanies heart failure.
Hyposecretion- Reduced secretion of ADH leads to a condition called as Diabetes insipidus .It is a condition where large amount of dilute urine is produced.This condition is not fatal as long as the thirst centre is functional. However problem arises when the person is unconscious or comatose . Such condition arises due to damage to the hypothalamus.
Hypersecretion-May occur due to hypothalamic injury, ecotopic ADH secreting tumors, general anesthesia, certain drugs.
The set of symptoms seen are collectively called as syndrome of inappropriate ADH secretion (SIADH).[22]
ADH levels are directly related to the solute concentration of blood. When encountered with highly osmotic fluid the osmo regulators loose fluid. They in turn send stimulus to the supra optic nucleus of the hypothalamus to release ADH.
When the solute concentration returns to normal the stimulus from osmo-regulators ceases and the ADH levels wane. Any factor that changes the solute concentration can influence ADH secretion.
- Stimulants to ADH include physical pain. low blood pressure, drugs like nicotine,morphine,babriturates etc.
- Inhibitors of ADH include alcohol and other diurectic drugs.20]
Normal ResultsNormal values -- 0 - 4.7 pg/mL
Note: pg/mL = picograms per milliliter [21]
DISORDERS:-
Heart failure is associated with what might be viewed as a paradoxical increase in AVP. Increased blood volume and atrial pressure associated with heart failure suggest that AVP secretion might be inhibited, but it is not. It may be that sympathetic and renin-angiotensin system activation in heart failure override the volume and low pressure cardiovascular receptors (as well as the hypothalamic control of AVP release) and cause an increase in AVP secretion. Nevertheless, this increase in AVP during heart failure may contribute to the increase in systemic vascular resistance as well as the enhanced renal retention of fluid that accompanies heart failure.
Hyposecretion- Reduced secretion of ADH leads to a condition called as Diabetes insipidus .It is a condition where large amount of dilute urine is produced.This condition is not fatal as long as the thirst centre is functional. However problem arises when the person is unconscious or comatose . Such condition arises due to damage to the hypothalamus.
Hypersecretion-May occur due to hypothalamic injury, ecotopic ADH secreting tumors, general anesthesia, certain drugs.
The set of symptoms seen are collectively called as syndrome of inappropriate ADH secretion (SIADH).[22]