salty sweat

Question

Why is the sweat more salty in a CF patient?

Answer

Cystic fibrosis or CF is an inheritable disease caused by a mutation in the CFTR gene (this is the genetic code containing the information to make the CFTR protein). The result is that the production of the correct CFTR protein is disturbed. This protein functions as a salt channel and in case of abnormal functioning or absence of the protein, chloride transplant outside the cell is diminished and resorption of sodium is increased. The cell will retain water and salt, resulting in abnormal sticky secretions in diverse places of the body where mucus is excreted.
The CFTR protein can be found on the mucosa of the airways, the secreting channels of the pancreas and the liver, spermal duct and sweat glands.
In the sweat glands sweat is produced. Initially this sweat has sodium and chloride concentration comparable to blood. While the sweat is transported through the sweat glands, part of the sodium and chloride is reabsorbed to the blood stream at least in non CF patients. For this reabsorption, the CFTR channel is needed. Since in CF patients the function of the CFTR protein is decreased or absent, the reabsorption of sodium and chloride will be decreased as well. The result is that the sweat of the CF patient has an abnormal high concentration of sodium and chloride. The amount of sweat remains the same and only the salt concentration is increased. The test to diagnose cystic fibrosis is based on the sweat analysis: sweat chloride is low in healthy persons and raised in case of cystic fibrosis.
Dr. P. Van De Wijdeven.

23.03.2010