Antidiuretic Hormone (ADH)/ Vasopressin Cell Communication By: Alejandra Ospina, Megan Campbell
General Information ` • Controls body water and solute concentration • The function of several hormones act on the kidneys and vascular system • Also known as Arganine Vasopressin • Produced by neurosecretory cells in the hypothalamus • Regulated by osmotic and volume stimuli • Water deprivation increases osmolality of plasma which activates hypothalmic osmoreceptors to stimulate ADH release
Gland • Secreted from the posterior pituitary gland • The hypothalamus sends signals to the pituitary gland to secrete the hormone. • Once hormone is secreted it goes to the kidney to put its purpose into effect.
Base & Structure • 9 amino acid structure sequence • Peptide based hormone • Hydrophilic – will not go into the cell • Binds with the receptor on the cell’s surface • Six of the amino acids form a ring structure, joined by disulfide bonds.
Pathway & Messenger • Vasopressin is released and binds to cell membrane at receptor • Binding results in ATP breaking down to cAMP • cAMP is the second messenger • cAMP activates PKA which synthesizes aquaporin • Aquaporins bind in the membrane and let H20 into the cell • Does not directly communicate with nucleus • Indirectly communicates with cytoplasm and cell membrane.
Pathway continued… • The receptor is linked to adenylyl cyclase (AC) enzymes via heterotrimeric G proteins in the membrane; thus, AC is activated as a consequence of VP binding to its V2 receptor resulting in the formation of the second messenger cyclic AMP. Subsequent phosphorylation of protein kinase A is associated with the final step of water reabsorption. Cyclic AMP is rapidly degraded to 5*-AMP by intracellular phosphodiesterase enzymes.
Pathway Diagram VP-vasopressin AQP- aquaporin PKA- protein kinase A
Cellular Response • Once cAMP is rapidly degraded by intracellular enzymes, thus the insertion of water channels into the membrane of the target cell, mediates rapid cross-membrane water transport. • There is also an increased movement of aggraphores towards these membranes. • The response is an increase of water absorption. • Not a transcription factor • It does turn an enzyme (protein kinase A) • There is no conformational change expect the introduction of more aquaporins into the membrane.
Positive or Negative Feedback? • Negative Feedback • Decreased water levels in body resulting in more ADH production- increased thirst- will increase the amount of aquaporins being added in increased as well (to reabsorb more water into the kidney) • Increased water levels result in a reduced ADH production telling the kidney to reabsorb less water.
Consequences of Disruption • When ADH is inhibited, water will not be reabsorbed at the tubules and the body will produce dilute urine. • Hyponatremia (not enough sodium (salt) in the body fluids outside the cells.) and hypo-osmolality resulting from inappropriate, continued secretion of the hormone despite normal or increased plasma volume, which results in impaired water excretion. • Symptoms: Confusion, disorientation, delirium, generalized muscle weakness, myoclonus, tremor, asterixis, hyporeflexia, ataxia, dysarthria, Cheyne-Stokes respiration, pathologic reflexes, generalized seizures, coma • Incontinence- involuntary urination: Common in elderly people. • Lack of ADH at night leads to bladder overfilling and thus urination.
Consequences of Disruption Continued… • Syndrome of inappropriate • antidiuretic hormone • secretion is also known as SIADH. • It is a condition where • your body makes too • much antidiuretic • hormone (ADH). • Increased ADH makes water remain inside your body, causing other chemicals in the blood such as salt may decrease. • Organs may not function properly
Consequences of Disruption Continued… • Hyperosmolality
Works Cited • http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/adh.html • http://joe.endocrinology-journals.org/content/159/3/361.full.pdf • http://images.google.com/ • http://emedicine.medscape.com/article/246650-overview • www.uic.edu/classes/phyb/phyb402dbh/lecture4.ppt • http://www.drugs.com/cg/syndrome-of-inappropriate-antidiuretic-hormone-secretion.html