HCO3 TRANSPORT AND CF
In this week's Nature (Vol. 410, No. 6824, 01 March 2001), Shmuel Muallem of the University of Texas Southwestern Medical Center, Dallas, and colleagues report that it is disruption in the transport of bicarbonate (HCO3-) ions, not chloride ions, in the lining of the lungs that may be responsible for causing Cystic Fibrosis (CF).
CF is caused by mutations in a protein called Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) which regulates the flow of negative ions in and out of the epithelial cells of the lung. So far, only the transport of chloride ions (Cl-) had been shown to be affected in patients with CF. Yet Cl- ions seem to have little role to play in causing the symptoms of CF which include the over production of thick mucus in the lungs an recurring bacterial infections.
Muallem and colleagues find that CFTR also plays an important role in the transport of bicarbonate (HCO3-) ions. Along with changes in pH in the cell secretions of CF patients, disrupted transport of HCO3- ions can lead to more viscous mucin and the ability of bacteria to bind to the lining of the lungs.
The researchers conclude that instead of trying to regulate the transport of Cl- ions in CF patients, enhancing the transport of HCO3- ions across cell membranes, or increasing the content of HCO3- in the epithelial cells of the lung may help ameliorate the symptoms of CF.
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