Lecture 19 Flashcards
NaK2Cl symporter:
uses the energy of the Na gradient to actively accumulate Cl above its electrochemical gradient.
In chlorine secretion, Na exits ___
via the basolateral Na-pump and K+ via channel
The transport of Cl across the epithelium induces ___
paracellular Na and water fluxes
What is the rate limiting step of chloride secretion?
the opening of the Cl- channel
Cl- channel is also
The CFTR
Secretory diarrhoea
-Caused by excessive stimulation of the secretory cells..
Enterotoxins:
irreversibly activate adenylate cyclase causing a maximal stimulation of CFTR which leads to a secretion that overwhelms the absorptive capacity
Oral rehydration therapy is used to treat:
secretory diarhoea.
Regulatory domain of CFTR:
When phosphorylated by protein kinase A, it acts like a plug and opens
Nucleotide binding domain of CFTR
Opens when ATP is binds to it to fully activate the channel. This must occur after the RD has been phosphorylated. This pore is closed by hydrolyising the ATP to ADP and dephosphorylating the RD so that ATP doesnt bind.
Normal lung epithelial cells vs CF in lungs
Normal has a balance between secretion and absorption, CF cells have a defective Cl- channel preveting isotonic fluid secretion and enhancing Na+ absorption, giving a dry lung surface.
People with cystic fibrosis have very ___
salty sweat
Two stages of sweat foramtion:
- A primary isotonic secretion of fluid by acinar cells.
- A secondary reabsorption of NaCl but not water produces a hypotonic solution.
The failure of epithelial cells in the ducts of sweat glands to reabsorb NaCl produces the salty sweat in CF patients.
In CF patients, CFTR is ____
defective, and Cl- accumulates in the duct lumen producing salty sweat.
