Fig. 5. SERCA pumps retard Ca²⁺ signal propagation in atrial myocytes. (A) A portion of the atrial myocyte examined. Ca²⁺ was recorded from a subsarcolemmal site (red circle), and also from a central non-regenerative region (black circle). (B) Summaries of the changes of the contraction amplitude (open black squares) and the subsarcolemmal/central Ca²⁺ gradient (filled green circles) observed upon acute application of 5 µM CPA (indicated by the black bar). (C) The characteristics of the Ca²⁺ signals observed in the cell before and during CPA application. The pseudo-linescan images in Caii and Cbii were obtained by sampling Ca²⁺ across the portion of the cell indicated by the dashed yellow line in A. The contraction of the cell before and during CPA application is shown in Caiii and Cbiii, respectively. Similar results were found in five cells (from three hearts).