Related Articles The effects of extracellular purines and pyrimidines on human airway smooth muscle cells. J Pharmacol Exp Ther. 2005 Nov;315(2):941-8 Authors: Govindaraju V, Martin JG, Maghni K, Ferraro P, Michoud MC Extracellular ATP and UTP modulate the function of many cell types through the stimulation of specific P2 receptors, and the inhalation of UTP has been proposed as a therapeutic means of increasing mucociliary clearance in cystic fibrosis patients. The aim of this study was to determine whether P2 receptors are present and functional in human airway smooth muscle (HASM) cells. Experiments were conducted on primary cultures of HASM cells. Reverse transcription-polymerase chain reaction and Western blot analysis showed that P2Y(1), P2Y(2), P2Y(4), and P2Y(6) receptor subtypes are expressed. Exposure to extracellular ATP, UTP, ADP, and UDP at concentrations ranging from 10(-6) to 10(-4) M, produced significant increases in intracellular Ca(2+) that peaked to 491 +/- 51 nM (p PMID: 16099930 [PubMed - indexed for MEDLINE]