The Associated Press

Scientists have gained new insight into how the lungs and other organs of cystic fibrosis patients become clogged with mucus or other secretions.

Researchers found a link between the severity of some forms of cystic fibrosis and the ability of a key protein to move particular molecules - bicarbonate ions - across cell membranes.

Up until recently, doctors thought that the symptoms were caused by the blocked movement of chloride ions. But the new research suggests bicarbonate ions also play a role.

The findings suggest that boosting bicarbonate flow in CF patients' crippled organs, including the lungs and pancreas, could lessen their disease. But how doctors might do that is still unclear.

Other researchers cautioned that the findings are intriguing but that it is too early to tell whether they could lead to any treatment.

``This provides one more piece of the CF puzzle,'' said Chris Penland, director of research for the Cystic Fibrosis Foundation.

Cystic fibrosis afflicts about 30,000 American children and young adults. The inherited disease attacks patients' lungs with a thick mucus, and most die from lung damage or infection. It also harms digestion and vitamin absorption by clogging organs such as the pancreas and intestines.

The disease is caused by defects in a particular gene that normally tells the body how to make a protein, known as CFTR, that helps shuttle chloride ions across cell membranes.

Most scientists believed until recently that cystic fibrosis was caused solely by CFTR mutations that prevented chloride ion movement.

But in recent years, scientists have found some cystic fibrosis sufferers with CFTR mutations that did not hamper chloride's movement.

Now, researchers at the University of Texas Southwestern Medical Center in Dallas have found CFTR mutations that hamper bicarbonate movement.

The findings appear in Thursday's issue of the journal Nature.

The Texas team, working with scientists at Yonsei University College of Medicine in Seoul, South Korea, studied 16 different CFTR mutations and found that those that caused more severe pancreatic disease also led to lower transport of bicarbonate.

Shmuel Muallem, a professor of physiology at the University of Texas who led the study, said the findings strongly suggest that bicarbonate secretion is crucial for the proper function of tissues affected by CF.

He said the disease's debilitating effects could possibly be reduced ``if we can learn how to deliver bicarbonate to the surface of the cells.''

Jeffrey Wine, director of the Cystic Fibrosis Research Laboratory at Stanford University, called the team's findings intriguing even though numerous questions remain.

``This shows convincingly that there is an effect on bicarbonate transport in these patients,'' he said.

Wine said the question now is what the precise biological mechanism behind that effect is. Knowing that is crucial to developing any new treatment, he said.

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