The best stimulator of Vasopressin includes
(D) Hypertonicity > Main stimulus for secretion of vasopressin is increased osmolality of plasma.> Reduced volume of extracellular fluid also has this effect, but is a less sensitive mechanism.> Serum osmolarity/osmolality is affected by vasopressin due to its role in keeping proper electrolytic balance in the blood stream.> mproper balance can lead to dehydration, alkalosis, acidosis or other life-threatening changes. The hormone ADH is partly responsible for this process by controlling the amount of water the body retains from the kidney when filtering the blood stream.# Vasopressin has three main effects:> Increasing the water permeability of distal convoluted tubule & collecting duct cells in the kidney, thus allowing water reabsorption & excretion of more concentrated urine, i.e., antidiuresis. This occurs through increased transcription and insertion of water channels (Aquaporin-2) into the apical membrane of distal convoluted 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. This effect is mediated by V2 receptors. Vasopressin also increases the concentration of calcium in the collecting duct cells, by episodic release from intracellular stores. Vasopressin, acting through cAMP, also increases transcription of the aquaporin-2 gene, thus increasing the total number of aquaporin-2 molecules in collecting duct cells.> Increasing permeability of the inner medullary portion of the collecting duct to urea by regulating the cell surface expression of urea transporters, 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.> Acute increase of sodium absorption across the ascending loop of Henle. This adds to the countercurrent multiplication which aids in proper water reabsorption later in the distal tubule and collecting duct.# Drug Stimulators of Vasopressin secretion: Vincristine, cyclophosphamide, tricyclic antidepressants, nicotine, epinephrine, and high doses of morphine. Lithium, which inhibits the renal effects of vasopressin, also enhances vasopressin secretion. Inhibitors of vasopressin secretion: Ethanol, phenytoin, low doses of morphine, glucocorticoids, fluphenazine, haloperidol, promethazine, oxilorphan, and butorphanol. Carbamazepine has a renal action to produce antidiuresis in patients with central diabetes insipidus but actually inhibits vasopressin secretion by a central action.
Decreased K+
Increased K+
Hypotonicity
Hypertonicity
Miscellaneous (Pharmacology)