Cystic Fibrosis Transmembrane Conductance Regulator- transports chloride ions across the epithelial cells. Mutations such as deletion, duplication and a few other types can cause Cystic Fibrosis. The movement of water in and out of the cells is either limited or blocked, as a result of this the mucus in the body is thicker and stickier than a normal persons.
In the late 1990's a commercial was aired warning parents that if they kissed their child and it tasted salty you should have them tested for CF. But why do people with CF secrete more salt in their sweat? How does the chloride levels in your sweat during a sweat test determine that you are positive for CF?
image taken from: http://cmr.asm.org
the arrows in the above diagram show paths taken by chloride ions during secretion. In both normal and CF sweat glands in the dermis, chloride is present in sercretions at a concentration that classifies them as isotonic (same solute concentration). The top portion of the sweat gland is normal, chloride is absorbed out of the sweat in a CFTR dependent manner as the sweat travels to the skin's surface from the gland. as a result, the chloride concentration in normal sweat is hypotonic. In the CF sweat gland, chloride absorption is hindered by defective CFTR functions. Because of this defect sweat that reaches the skins surfaces has higher than normal concentrations.
Stay salty,
B.
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