Washington: American scientists have found taste receptors in human lungs similar to those on the tongue, a discovery which they say could revolutionise the treatment of asthma and other obstructive lung diseases.
University of Maryland researchers who accidentally found the taste receptors in the lungs said they play a key role in regulating 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 detection of functioning taste receptors on smooth muscle of the bronchus in the lungs was so unexpected that we were at first quite sceptical ourselves," said study`s senior author Stephen Liggett, a professor of medicine and physiology at the University of Maryland School of Medicine.
Dr Liggett, whose team found the taste receptors by accident during an unrelated study of human lung muscle receptors, said the taste receptors in the lungs are the same as those on the tongue.
While the tongue`s receptors are clustered in taste buds that send signals to the brain, the receptors in the lungs are not clustered in buds and do not send any signal to the brain, yet they respond to substances that have a bitter taste.
For their study, published online in Nature Medicine, Dr Liggett and his team exposed bitter-tasting compounds to human and mouse airways, individual airway smooth muscle cells, and to mice with asthma.
They found that the bitter compounds opened the airway more profoundly than any known drug used for treating asthma could have.
According to the researchers, 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 team tested a few standard bitter substances known to activate these receptors. "It turns out that the bitter compounds worked the opposite way from what we thought," said
"They all opened the airway more profoundly than any known drug that we have for treatment of asthma or chronic obstructive pulmonary disease (COPD)."