کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
2190863 | 1097827 | 2011 | 8 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Complex and rate-dependent beat-to-beat variations in Ca2+ transients of canine Purkinje cells Complex and rate-dependent beat-to-beat variations in Ca2+ transients of canine Purkinje cells](/preview/png/2190863.png)
Purkinje fibers play an essential role in transmitting electrical impulses through the heart, but they may also serve as triggers for arrhythmias linked to defective intracellular calcium (Ca2+) regulation. Although prior studies have extensively characterized spontaneous Ca2+ release in nondriven Purkinje cells, little attention has been paid to rate-dependent changes in Ca2+ transients. Therefore we explored the behaviors of Ca2+ transients at pacing rates ranging from 0.125 to 3 Hz in single canine Purkinje cells loaded with fluo3 and imaged with a confocal microscope. The experiments uncovered the following novel aspects of Ca2+ regulation in Purkinje cells: 1) the cells exhibit a negative Ca2+–frequency relationship (at 2.5 Hz, Ca2+ transient amplitude was 66 ± 6% smaller than that at 0.125 Hz); 2) sarcoplasmic reticulum (SR) Ca2+ release occurs as a propagating wave at very low rates but is localized near the cell membrane at higher rates; 3) SR Ca2+ load declines modestly (10 ± 5%) with an increase in pacing rate from 0.125 Hz to 2.5 Hz; 4) Ca2+ transients show considerable beat-to-beat variability, with greater variability occurring at higher pacing rates. Analysis of beat-to-beat variability suggests that it can be accounted for by stochastic triggering of local Ca2+ release events. Consistent with this hypothesis, an increase in triggering probability caused a decrease in the relative variability. These results offer new insight into how Ca2+ release is normally regulated in Purkinje cells and provide clues regarding how disruptions in this regulation may lead to deleterious consequences such as arrhythmias.
Research Highlights
► Canine cardiac Purkinje cells show a negative Ca2+ frequency relationship.
► Slow pacing causes Ca2+ wave propagation from the cell periphery to the center.
► Local Ca2+ transients show beat-to-beat variability with greater variability at faster pacing rates.
► Stochastic triggering of local Ca2+ release is responsible for the beat-to-beat variability.
Journal: Journal of Molecular and Cellular Cardiology - Volume 50, Issue 4, April 2011, Pages 662–669