Traffic across epithelial cells: Chloride secretion

Question 1

Describe secretion of CL across the epithelial tissue

Steps 1-3

Answer 1

1. tight jumctions divide apical and basal domains
2. Na pump creates an ion gradient
3. NaK2CI symporter uses the conc gradient to accumulate CI above the conc gradient (basal end)

Question 2

Describe secretion for CI across the epithelial tissue

Steps 4-6

Answer 2

4. CI leaves the epithelial cells via passive diffusion (apical)
5. Na accumated within the cell leaves via Na pump and basolateral domain
6. influx of CI across the epithelium causes a increase in water (paracellular)

Question 3

Over stimulation of cystic fibrosis transmembrane regulator causes what

Answer 3

causes diarhea and cystic fibrosis

Question 4

Describe a CI channel

Answer 4

regulated
named a cystic fibrosis transmembrane regulator

are ion gated channels

Question 5

In secretory diarrhoea what does a enterocyte activate

Answer 5

adenylate cyclase

Question 6

what is secretory diarrhoea caused by

Answer 6

excess stimulation of secretory cells in the crypts of the small intestine of colon

increase stimulation= a high conc of secretagogues by tumors or inflammation

Question 7

What are enterotoxins involvement with secretory diarrhoea

Answer 7

enterotoxins activate adenylate cyclase causing maximal stimulation of CFTR= overwhelms absorptive capacity of colon

Question 8

what is CFTR regulated by

Answer 8

protein kinase A dependent phosphorlylation of the R domain and binding of ATP to the NBD

Question 9

What occurs in the epithelial cell in CF

Answer 9

defective CI channel prevents isotonic fluid secretion and enhances Na absorption to give a dry lung surface

Question 10

What is the pathology of CI secretion

Answer 10

CFTR gene defect

defective ion transport

airway surface liquid

defective mucocillary clearance

mucus obstruction

inflammation

infection

Question 11

What is cystic fibrosis involvement with sweat

Answer 11

failure of epithelial cell in the duct of sweat glands to reabsorb NaCI produces salty sweat in CF