LCR emergence with respect to the global Ca2+ transient peak, global Ca2+ nadir, and formation of ‘Late Diastolic Ca2+ Elevation’ (LDCaE).
A: Examples of how the whole cell global Ca2+ fluorescence signal recorded (red waveform trace) varies with time over three arbitrarily selected consecutive diastolic periods from a single cell. It can be seen that there are approximately rhythmical peaks and troughs in the spatially-averaged whole cell Ca2+ fluorescence. Horizontal ‘span’ bars represent the duration of individual LCRs, from their appearance to disappearance. LCRs are further categorized into early (labeled in green) and late (labeled in magenta), depending on when they begin with respect to the whole cell spatially averaged Ca2+ fluorescence trace (an early LCR begins before global Ca2+ nadir (blue broken line), a late LCR begins after the nadir). The waxing LCR number and intensity with time leads to the LDCaE (Late Diastolic Ca2+ Elevation), and a prominent increase in rate of rise of Ca2+ fluorescence (black curved arrows). B: Illustration of individual LCR signals. In each of the three diastolic periods illustrated in A, the global Ca2+ transient signal (blue dashed line) is plotted along with the local Ca2+ fluorescence signal for selected early-, average- and late-occurring local LCRs, to illustrate how the local Ca2+ signal varies with respect to the whole cell signal. C: Bar chart to demonstrate how LCR number varies in all of the diastolic intervals studied (data from 9 cells). D: Bar chart demonstrating the mean number of early and late LCRs per diastole, showing that numbers of early and late diastoles are approximately equal across all the diastolic intervals studied.