Response to Article about Cystic Fibrosis Essay -- Biology

Cystic Fibrosis - Summary of Article It has been known for quite some time that CFTR is a cAMP regulated chloride ion channel whose mutation is intimately linked to cystic fibrosis (CF). However, the abnormality in the chloride ion channels is not the only biochemical peculiarity associated with the disease. Of particular interest to researchers is the finding that sodium ion (Na+) absorption in the cells of CF patients is both elevated and positively related to the cAMP concentration, whereas, in normal cells, cAMP concentration is inversely related to the rate of Na+ absorption. The malfunction of the Na+ pump becomes immediately apparent, for the primary symptom of CF is a chronic bacterial infection of the lungs, due to the abnormally low viscosity of the fluid which bathes the cellular epithelium; by pumping ions into the airway, rather than into the cell, a thermodynamically unfavorable concentration gradient of sodium ions is is established, in which the airway is hypotonic and osmosis is kinetically favored. In the case of CF, the local chloride pump is inoperative, and the sodium pumps are incredibly overactive, importing Na+ from the airway, and taking water out of the fluid inside the lungs in the process. Therefore, is is inappropriate to place the sole responsibility for the low fluid viscosity directly upon the mutation of the CFTR protein. Studies have demonstrated that the elevated Na+ absorption is not due to an overexpression of the Na+ transport protein, ENaC, in the membrane, nor can cAMP sensitivity be linked to a genetically mutated ENaC. The possibility that the altered CFTR indirectly led to the Na+ channel phenomena by altering the functionality of normal ENaC formed the basis of a hypothesis which ... ...The use of amiloride as a form of treatment is significant because amiloride actually helps the body in correcting the chloride and sodium ion concentration, thereby rehydrating the cells and thinning the mucus. This process differs from current treatments which loosen the mucus or dilute it so the patients can rids their lungs of the infectious substance more easily. Works Cited 1.) Purves, WK, Orians GH, Heller HC. Life: the Science of Biology. Sunderland: Sinauer Associates, Inc.; 1995. Chapter 15, Genetic Disease and Modern Medicine; pages 334-352. 2.) "CF-FAQ Part 1." Ed. Ron Trueworthy. CF-WEB. Internet. 10 September 1996. 3.) S. H. Wright, interview by group members. Tucson, Arizona, 22 October 1996. 4.) M. J. Stutts, C. M. Canessa, J. C. Olsen, M. Hamrick, J. A. Cohn, B. C. Rossier, R. C. Boucher, Science, v. 269, 11 August 1995, pages 847-850.