Luckily, there is a second, "rescue" chloride channel that can take up some of the slack for cystic fibrosis patients.
"When people get cystic fibrosis, they don't just die after birth. The rescue channel keeps them limping on and provides enough hydration," Tarran explained. "The hypothesis is that that's OK until there's a catastrophic event like a viral infection."
Tarran and his colleagues hypothesized that estrogen might affect chloride secretion, thus explaining more severe illness in women. They measured the ability of chloride to move in and out of cells in women with cystic fibrosis who were not taking any birth control or other hormonal treatments.
While estrogen was low, there was no effect on the nasal passages. But high levels of estrogen while a woman was ovulating inhibited the rescue channel by about 50 percent.
"For a normal woman, it's no big deal because the other, huge channel is doing its job," Tarran said. "But in cystic fibrosis it is a big deal. The airway is cut by half, so maybe for four to five days each month there is a reduced ability to hydrate the airways. For a few days every month, it becomes a statistical lottery, if you happen to breathe in something nasty on those days."
Tarran's group next plans to test lung function in healthy women taking tamoxifen, the breast cancer drug that interferes with the activity of estrogen.
Dr. John Saito is assistant professor of pediatrics at Texas A&M Health Science Center College of Medicine, and director of the Cystic Fibrosis Center at Scott & White Hospital. "Everyone has suspected differences but nailing this down is difficult to do. This [new research] offers some insight as
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