A genetic discovery in electric ray fish may shed new light on cystic fibrosis in humans and help the search for drugs against the common, inherited fatal disease, researchers reported this week.

German scientists said they have identified and duplicated a gene that codes for production of a protein that regulates the flow of salt in and out of cells of electric rays.That finding could have important implications for cystic fibrosis patients because defective salt regulation is a central feature of the disorder, in which thick mucus clogs the lungs and leads to life-threatening infections. About one in 2,000 white babies are stricken by cystic fibrosis, and most patients die before age 40.

Last year, researchers pinpointed the genetic flaw that causes about 70 percent of cystic fibrosis cases. But contrary to expectations, the affected gene did not code for production of a salt gateway, called a chloride channel. Instead, researchers suspect the gene codes for a channel for another type of molecule, which in turn regulates chloride traffic through another, undiscovered channel.

Chloride - which is a component of salt - helps regulate cells' water balance, and upsetting that balance may be what causes the mucus of cystic fibrosis patients to thicken.

In a study published in the journal Nature, Thomas Jentsch and colleagues from Hamburg University said they were able to find the gene for chloride channels in so-called torpedo rays with almost no knowledge of what type of gene or protein for which they were searching. The protein does not resemble any other channel yet discovered in cell membranes.

Torpedo rays, which are bottom-dwelling, slow-moving fish that look somewhat like stingrays, use their electric organs to produce shocks of about 100 volts to stun their prey. The rays were chosen for the study because their ability to generate relatively large electric currents hinges on extremely high concentrations of cells rich in chloride channels.