Objective:To explore the interaction between Calcineurin and TRPC6, and the impact of this interaction on endothelin－1(ET－1)－induced proliferation of pulmonary artery smooth muscle cells (PASMCs). Methods:PASMCs were treated with ET－1 to stimulate their proliferation with or without prior treatment of CsA or TRPC6 siRNA. Calcineurin activity in the cells was measured using a calcineurin activity assay kit,and TRPC6 expression was examined using Western blotting and RT－PCR. PASMCs proliferation following the treatments was determined using MTT assay. Results:ET－1 activited Calcineurin activity and upregulated TRPC6 expression. TRPC6 expression was decreased in response to the CsA treatment. Calcineurin activity was attenuated after pretreatment with TRPC6 siRNA;however,ET－1－stimulated PASMCs proliferation was inhibited after pretreatment with both CsA and TRPC6 siRNA. Conclusion:Calcineurin and TRPC6 are involved in ET－1－induced proliferation in PASMCs,and the interaction existes between Calcineurin and TRPC6 in PASMCs.