Anti-diuretic hormone Flashcards
anti-diuretic hormone
synthesised by the supra-optic nucleus of the hypothalamus and stored in the posterior pituitary
anti-diuretic hormone is secreted in response to
- hypotension which causes production of angiotensin II, hypothalamus has angiotensin II receptors so when angiotensin II production increases the hypothalamus increases its production and secretion of anti-diuretic hormone
- increased serum osmolarity= when the plasma is hypertonic the hypothalamus has osmoreceptors which are stimulated to release anti-diuretic hormone
anti-diuretic hormone is also known as
vasopressin
ADH is released into the circulation in respsone to hypotension or increased serum osmolarity and it
binds to vasopressin-2-receptors on the base-lateral membrane of the principal cells, this activates G-stimulatory protein which activates adenylate cyclase which converts ATP to cAMP which activates protein Kinase A
protein Kinase A then
simulates the formation of vesicles which contain aquapoin type 2 and also causes the vesicles it has created to fuse with the apical membrane of the principal cells which allows water to be re-absorbed into the cell from the tubule
once water is within the cell
it passes into the blood through type 3 and type 4 aquaporins on the baso-lateral membrane
anti-diuretic hormone also binds to
vasopressin type 1 receptos (V1) which are present on any systemic blood vessel this causes the smooth muscle of the blood vessel to contract causing vasoconstriction which increases total peripheral resistance which increases systemic blood pressure
so what would happen if you don’t make enough ADH (i.e. vasopressin)
known as central diabetes insidious where the hypothalamus does not create or release vasopressin
causes of central diabetes insidious
head trauma, iatrogenic, wolfram syndrome
in central diabetes insipidus
because vasopressin is not present in the circulation there is not formation of aquaporin type 2 receptor on the apical membrane of the principal cells therefore, no water is re-absorbed so excessive amounts of water are excreted which reduces the urine osmolarity and causing polyuria and increases the plasma osmolarity causing excessive thirst
treatment of central diabetes insipidus
desmopressin (synthetic anti-diuretic hormone)
nephrogenic diabetes insipidus
inability of the nephron to respond to the vasopressin that has been produced by the hypothalamus
causes of nephrogenic diabetes insipidus
- X-linked recessive mutation in the V2 receptor gene (AVPR-2)
- LITHIUM
- DEMELOCYCLINE which is an antibiotic used to block the excessive release of vasopressin by tumours
examples of vasopressin analogues
desmopressin and terlipressin
vasopressin analogues are used in
central diabetes insipidus, bedwetting/ nocturnal enuresis in children over 10, to control vatical bleeding in portal hypertension
