A3 Adenosine Receptor is a widely expressed receptor that mediates the multiple functions of adenosine. For example, this receptor is believed to mediate the protective effect of adenosine released during cardiac ischemia. In lungs, the receptor mediates inhibition of eosinophil chemotaxis and may be useful in the treatment of eosinophil-dependent diseases such as asthma and rhinitis. Adenosine A3 Receptor has been reported mostly in brain, lung, liver, heart, kidney, and testis. ESTs have been isolated from heart/melanocyte/uterus, kidney, pituitary, and placenta libraries.