Taste receptors in the lungs? Researchers at the University of Maryland School of Medicine in Baltimore have discovered that bitter taste receptors are not just located in the mouth but also in human lungs. What they learned about the role of the receptors could revolutionize the treatment of asthma and other obstructive lung diseases.
"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," says the study's senior author, Stephen B. Liggett, M.D., professor of medicine and physiology at the University of Maryland School of Medicine and director of its Cardiopulmonary Genomics Program.
Dr. Liggett, a pulmonologist, says his team found the taste receptors by accident, during an earlier, unrelated study of human lung muscle receptors that regulate airway contraction and relaxation. The airways are the pathways that move air in and out of the lungs, one of several critical steps in the process of delivering oxygen to cells throughout the body. In asthma, the smooth muscle airways contract or tighten, impeding the flow of air, causing wheezing and shortness of breath.
The 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. The researchers say that in the lung, 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.
For the current study, Dr. Liggett's team exposed bitter-tasting compounds to human and mouse airways, individual airway smooth muscle cells, and to mice with asthma. The findings are published online in Nature Medicine.
Most plant-based poisons are bitter, so the researchers thought the purpose of the lung's taste receptors was similar to those in the tongue to warn against poisons. "I initially thought the bitter-
|Contact: Sharon Boston|
University of Maryland Medical Center