OBJECTIVE: Stretch increases protein synthesis and contractility of the vascular wall. We investigated the role of calcium inflow in this response. METHODS: Western blot, [³⁵S]methionine incorporation, siRNA transfection, real time RT-PCR and confocal microscopy on organ-cultured mouse portal vein or primary portal vein cells. RESULTS: Synthesis of contractile and cytoskeletal proteins, marking the contractile phenotype, was inhibited by the L-type channel blocker verapamil (1 mm) and promoted by the agonist Bay K8644 (1 mm). Cofilin-2 phosphorylation changed in parallel, indicating that voltage-dependent Ca²⁺ entry (VDCE) stimulates Rho-dependent actin polymerisation. In contrast, global protein synthesis was inhibited by blockade of store- operated Ca²⁺ entry (SOCE) using 2-aminoethoxydiphenyl borate (2-APB; 30 mm) but not affected by verapamil or Bay K 8644. 2-APB had no effect on cofilin phosphorylation and increased the relative rate of smooth muscle marker synthesis. Hyperpolarisation by the K⁺ channel opener levcromakalim (10 mM) inhibited stretch-related responses. Activation of VDCE in portal vein cells by KCl (60 mM) caused RhoA translocation followed by phosphorylation of LIMK-2 and cofilin-2. VDCE also increased mRNA expression of mycyte enhancer factor (MEF2), myocardin, and smooth muscle marker genes, which was abrogated by verapamil (5 mM) or the Rho kinase inhibitor Y27632 (10 mM). MEF2 knock-down eliminated Ca²⁺ sensitivity of myocardin expression. SOCE elicited by thapsigargin (100 nM) increased ERK1/2 phosphorylation and c-fos mRNA expression, while exerting no effect on either phosphorylation of LIMK-2 and cofilin-2 or mRNA expression of myocardin and MEF2. CONCLUSIONS: VDCE and stretch stimulate smooth muscle differentiation, while SOCE stimulates growth. Increase of TRPC1 channels, supporting SOCE, and decreased expression of L-type channels in vascular injury may induce dedifferentiation and growth/proliferation of vascular smooth muscle cells.