"The detection of functioning taste receptors on smooth muscle of the bronchus in the lungs was so unexpected that we were at first quite skeptical ourselves," said lead study author Stephen Liggett, M.D., a professor of medicine and physiology at the University of Maryland School of Medicine, in a press release.
His team accidentally found the taste receptors during an earlier, unrelated study of human lung muscle receptors that regulate airway contraction and relaxation, he said.
Taste receptors in the lungs are the same as those on the tongue. The tongue's receptors are clustered in taste buds, which send signals to the brain. In the lungs, the taste receptors are not clustered in buds and do not send signals to the brain, yet they respond to substances that have a bitter taste, the researchers noted.
Most plant-based poisons are bitter, so the researchers thought the purpose of the lung's taste receptors was similar to those on the tongue -- to warn against poisons. There are thousands of compounds that activate the body's bitter taste receptors but are not toxic in appropriate doses. Many are synthetic agents, developed for different purposes, and others come from natural origins, such as certain vegetables, flowers, berries, and trees, the researchers found.
For the current study, Dr. Liggett's team exposed bitter-tasting compounds to human and mouse airways, individual airway smooth muscle cells, and mice with asthma.
"It turns out that the bitter compounds worked the opposite way from what we thought," Dr. Liggett said. "They all opened the airway more extensively than any known drug that we have for treatment of asthma or chronic obstructive pulmonary disease."
This observation could have implications for new therapies, he noted. "New drugs to treat asthma, emphysema, or chronic bronchitis are needed," he said. "This could replace or enhance what is now in use, and represents a completely new approach."
Copyright © 2010 DrBicuspid.com