托福阅读背景知识之肺部有味觉

　　在以往的研究中，人们认为人体的味觉器官并不包括肺部，但是最新一项研究却发现肺部肌肉有“品尝”苦味的功能。下面，就请跟小编一起进入今天的托福阅读材料：肺部有味觉。

　　Take a deep breath. Taste anything? Actually, your lungs may. Becausescientists have discovered that the same receptors that exist on the tongue totaste bitter substances are also found on the smooth muscle of the lungs.

　　Researchers were studying the receptors on smooth lung muscles thatregulate contraction and relaxation of theairways. That’s when they made thediscovery—which was so unexpected that the researchers themselves wereskeptical.

　　Finally, they became convinced that the receptors were really there, thoughnot clustered in taste buds as they are on the tongue. The scientists thenexposed human and mouse airways to various bitter compounds to gauge theeffects.

　　Many toxic compounds are bitter, so the researchers expected the lungmuscle to tense up and contract—to compel the breather to move away fromwhatever was bitter and perhaps toxic. But, in a second surprise, bittercompounds relaxed and opened airways better than any existing asthma drug. Thestudy is in the journal Nature Medicine. "Bitter taste receptors on airwaysmooth muscle bronchodilate by localized calcium signaling and reverseobstruction".

　　Researchers will continue to search for the role of the receptors.Meanwhile, the work represents a surprising new lead in the search for drugs totreat asthma, emphysema or chronic bronchitis.—Cynthia Graber