Antidiuretic Hormone (ADH)/ Vasopressin

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Antidiuretic Hormone (ADH)/ Vasopressin

• Cell Communication
• By Alejandra Ospina, Megan Campbell

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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

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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.

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Base Structure

• 9 amino acid structure sequence
• Peptide based hormone
• Hydrophilic will not go into the cell
• Binds with the receptor on the cells surface
• Six of the amino acids form a ring structure,
  joined by disulfide bonds.

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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.

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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.

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Pathway Diagram
VP-vasopressin AQP- aquaporin PKA- protein kinase
A
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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.

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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.

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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.

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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

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Consequences of Disruption Continued

• Hyperosmolality

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Works Cited

• http//www.vivo.colostate.edu/hbooks/pathphys/endo
  crine/hypopit/adh.html
• http//joe.endocrinology-journals.org/content/159/
  3/361.full.pdf
• http//images.google.com/
• http//emedicine.medscape.com/article/246650-overv
  iew
• www.uic.edu/classes/phyb/phyb402dbh/lecture4.ppt
• http//www.drugs.com/cg/syndrome-of-inappropriate-
  antidiuretic-hormone-secretion.html