The role of Ca 2؉ influx in the regulation of the sarcoendoplasmic reticulum Ca 2؉ ATPases (SERCA) associated with intracellular Ca 2؉ pools was investigated during smooth muscle cell (SMC) proliferation induced by platelet-derived growth factor (PDGF). We first defined that the previously described up-regulation of the SERCA2a isoform found in vascular SMC after a 24-h stimulation with PDGF (Magnier, C., Papp, B., Corvazier, E., Bredoux, R., Wuytack, F., Eggermont, F., Maclouf, J., and Enouf, J. (