Transient receptor potential (TRP) cation channels are a critical pathway for Ca2+entry during pulmonary artery (PA) smooth muscle contraction. However, whether canonical TRP (TRPC) subunits and which TRP channel isoforms are involved in store depletion-induced pulmonary vasoconstriction in vivo remain unclear. This study was designed to test whether overexpression of the human TRPC1 gene ( hTRPC1) in rat PA enhances pulmonary vasoconstriction due to store depletion-mediated Ca2+influx. The hTRPC1 was infected into rat PA rings with an adenoviral vector. RT-PCR and Western blot analyses confirmed the mRNA and protein expression of hTRPC1 in the arterial rings. The amplitude of active tension induced by 40 mM K+(40K) in PA rings infected with an empty adenoviral vector (647 ± 88 mg/mg) was similar to that in PA rings infected with hTRPC1 (703 ± 123 mg/mg, P = 0.3). However, the active tension due to capacitative Ca2+entry (CCE) induced by cyclopiazonic acid was significantly enhanced in PA rings overexpressing hTRPC1 (91 ± 13% of 40K-induced contraction) compared with rings infected with an empty adenoviral vector (61 ± 14%, P < 0.001). Endothelial expression of hTRPC1 was not involved since the CCE-induced vasoconstriction was also enhanced in endothelium-denuded PA rings infected with the adenoviral vector carrying hTRPC1. These observations demonstrate that hTRPC1 is an important Ca2+-permeable channel that mediates pulmonary vasoconstriction when PA smooth muscle cell intracellular Ca2+stores are depleted.