Cellular Processes [Chloride Secretion] Flashcards
Description of Chloride Secretion (include the transporter, sodium)
A cotransporter in the basolateral membrane accumulated Cl- above its gradient. This enables it to leave the cell via a channel in the apical membrane. Sodium moves paracellular w H2O to preserve electroneutrality.
Step 2 of chloride secretion
Sodium pump sets up ion gradients
Step 3 chloride secretion
The NaK2Cl symporter uses the energy of the Na+ gradient to actively accumulate Cl above conc gradient.
Entry step.
Step 4 chloride secretion
Cl- leaves the cell by passive diffusion through an ion channel.
Exit step.
Step 5 chloride secretion
Na+ exits via the basolateral sodium pump and K+ exits via its channel.
This makes the gradient more -ve, attracting Cl.
Step 6 chloride secretion
Cl- transport induces Na+ and H2O movement paracellular into the lumen.
How is cystic fibrosis caused?
Chloride channel responsible for Cl exit is defective.
The two stages of sweat formation
- Primary isotonic fluid secretion by acinar cells.
2. Secondary reabsorption of NaCl to produce a hypotonic solution.
How is cystic fibrosis sweat formation different?
The failure of epithelial cells in the ducts of sweat glands to reabsorb NaCl produces salty sweat.
4 ways of clinical management for cystic fibrosis
Chest percussion
Antibiotics
Pancreatic enzyme replacement
Nutrition
Cystic fibrosis - airways
Clogging and infection of bronchial passages. Can cause lung disease.
Cystic fibrosis - liver
Plugging of small bile ducts impedes digestion in 5% of patients
Cystic fibrosis - pancreas
Occulusion of ducts prevents the pancreas delivering enzymes for digestion to the bowel. Can diabetes.
Cystic fibrosis - small intestine
Obstruction of the gut by thick stool. Surgery in newborns.
Cystic fibrosis - reproductive tract
Absence of fine ducts. Infertile. Occasionally women’s mucus blocks sperm.
Effect of cystic fibrosis on the lungs specifically
Dry. Mucus thick. Bacteria proliferate and attract immune cells which damages tissue. DNA released from bacteria and lung cells.
How does the chloride channel work?
Regulated by protein kinase A. Phosphorylation of R domain and binding of ATP to NBD. ATP causes R domain to move, letting ions come down gradient.
