The functional expression of extracellular calcium-sensing receptor in rat pulmonary artery smooth muscle cells

BACKGROUND: The extracellular calcium-sensing receptor (CaSR) belongs to family C of the G protein coupled receptors. Whether the CaSR is expressed in the pulmonary artery (PA) is unknown. METHODS: The expression and distribution of CaSR were detected by RT-PCR, Western blotting and immunofluorescence. PA tension was detected by the pulmonary arterial ring technique, and the intracellular calcium concentration ([Ca(2+)](i)) was detected by a laser-scanning confocal microscope. RESULTS: The expressions of CaSR mRNA and protein were found in both rat pulmonary artery smooth muscle cells (PASMCs) and PAs. Increased levels of [Ca(2+)](o )(extracellular calcium concentration) or Gd(3+ )(an agonist of CaSR) induced an increase of [Ca(2+)](i )and PAs constriction in a concentration-dependent manner(. )In addition, the above-mentioned effects of Ca(2+ )and Gd(3+ )were inhibited by U73122 (specific inhibitor of PLC), 2-APB (specific antagonist of IP(3 )receptor), and thapsigargin (blocker of sarcoplasmic reticulum calcium ATPase). CONCLUSIONS: CaSR is expressed in rat PASMCs, and is involved in regulation of PA tension by increasing [Ca(2+)](i )through G-PLC-IP(3 )pathway.