Lecture 23 Flashcards
Where is vasopressin produced?
in the hypothalamus
Where is vasopressin stored and released from?
The posterior pituitary gland
Where does vasopressin bind and to which receptor?
It binds to the vasopressin receptor (V2) on the basolateral membrane of LDT and CD cells
What is the effect of vasopressin binding to its receptor on the cells of the LDT and CD?
Results in incorporation of AQP2 channels
into the apical membrane = increase H2O flow
How long does it take AQP2 to appear in the apical membrane of cells of the LDT and CD after vasopressin binds to the V2 receptor?
30-40mins
What are the osmoreceptors that detect the changes?
The osmoreceptors in the hypothalamus stimulate the process of the ADH release. Macula densa cells in the thick ascending limb monitor Na+ to control H2O balance
What happens when vasopressin binds to its V2 receptor?
The GPCR activates adenylate cyclase which converts ATP to cAMP which activates PKA and this initiates the movement of vesicles out to the membrane
What are 5 symptoms of diabetes insipidus?
- ________ - large volume - _________ urine(>15L/d)
- ________ - excessive __________
- First year of life - v________, f______, slow g________, developmental ________
- Severe ________
- Severe cases - mental _________ due to dehydration of the ______–
- Polyuria - large volume - hypotonic urine(>15L/d)
- Polydipsia - excessive drinking
- First year of life - vomiting, fever, slow growth, developmental delay
- Severe dehydration
- Severe cases - mental deficiency due to dehydration of the brain
What are the two types of diabetes insipidus?
Central/neurogenic diabetes insipidus
Nephrogenic diabetes insipidus
Describe CDI
this is due to a lack of production of vasopressin by the hypothalamus due to a problem with the supraoptic or paraventricular nuclei or release from the posterior pituitary gland
Describe NDI
This is a problem at the level of the kidney
What are the two types of NDI? What causes each of these?
- congenital X-linked NDI: due to a mutated V2
receptor which occurs in 90% of NDI patients (normally males) - autosomal NDI: due to mutated AQP2 channel which occurs in 10% of NDI patients (there is normal V2 function)
How many mutations in the V2 receptor can result in congenital NDI?
200
What mutations cause autosomal NDI
the mutations in the NPA boxes (aparagine-proline-alanine) or in the pore itself
Mutations of the V2 receptor can arise in a number of different ways:
• non-functional ________ channels and _______ receptors
• ineffective ________ of _________ (AQP2 or V2)
• simple binding _________ of V2 receptors
• intracellular _________ problems (AQP2 or V2)
• accelerated ________ of AQP2 channel or V2 receptor to the _________ or ___________
- non-functional AQP2 channels and V2 receptors
- ineffective biosynthesis of protein (AQP2 or V2)
- simple binding impairment of V2 receptors
- intracellular trafficking problems (AQP2 or V2)
- accelerated degradation of AQP2 channel or V2 receptor to the proteasome or lysosome