Answer:
Ion channel dysfunction
1) altered Cl- secretion in submucous glands,
2) increased Na+ absorption and consequent electrolytes hyperabsorption in the superficial epithelium.
Explanation:
The normal function of the CFTR protein is to transport Cl- ions as it works a chlorine channel regulated by AMPc and by protein kinase K (PKA). CFTR is also a regulator for other ionic channels.
The CFTR protein expresses in the luminal portion of the secretory and absorptive epithelial membranes. It has a significant role in the secretion of electrolytes activated by AMPc and intracellular calcium. This protein constitutes the way out of Cl- from the lumen. CFTR protein also regulates electrolyte function. It inhibits the epithelial Na+ channel of absorptive epithelial cells from the colon and aerial vias. It also activates the Na+ channel in sudoriparous ducts.
Given that defects in the CFTR protein take to a defective regulation in the Na+ channel, cystic fibrosis characterizes by alterations in electrolytes secretions and absorption. There are two significant physiopathological mechanisms:
1) altered Cl- secretion in submucous glands,
2) increased Na+ absorption and consequent electrolytes hyperabsorption in the superficial epithelium.
Patients with cystic fibrosis are incapable of increasing their secretory transport. Three events impede the higher osmotic transepithelial gradient:
- the increased epithelial conductance to Na+ in apical membranes,
- the paracellular permeability to Cl- and
- high permeability to water.
This leads to hyperabsorption in the patient epitheliums. The superficial liquid layer in the aerial vias decreases, mucous glands are not released from the mucus, and the mucociliary clearance is strongly altered in aerial vias.
