Table 3

Intracellular Ca2+ signalling in LV cardiomyocytes, Ca2+ transients and cell shortening

ShamPMIBNP-PMIBB-PMIBB-BNP-PMI
Ca2+ transient (Indo1-AM)
Amplitude (F405 to F480)5.24±0.184.47±0.25*4.12±0.09†5.3±0.11§5.81±0.16*,||,¶
τ (ms)294±21371±15*361±17*312±18§262±19||,#
SR-Ca2+ content (F405 to F480)9.3±0.47.2±0.1*6.4±0.3†,§8.6±0.3§9.6±0.2||,#
Diastolic Ca2+ level (F405 to F480)0.55±0.010.65±0.02†0.71±0.01‡0.51±0.02||0.50±0.01||
Sarcomere shortening (%)9.65±0.327.21±0.35†7.06±0.34†9.16±0.31§10.41±0.29||,#
Arrhythmic cells (%)7.1±5.472.3±14.4‡62.9±9.7‡24.4±3.3*,¶11.6±4.9¶,#
Ca2+ sparks (Fluo4-AM)
Frequency (Events.100/µm/S)1.05±0.055.12±0.23†6.34±0.13†,§1.84±0.14*,||1.04±0.27¶,#
Amplitude (ΔF/F0)0.58±0.010.49±0.02*0.41±0.01†,||0.54±0.01§0.61±0.01¶,#
FDHM (ms)14.3±0.423.7±1.2†34.3±2.1†,||16.9±1.7*,§11.1±1.1¶,#
FWHM (ms)1.34±0.021.67±0.05*2.10±0.06†1.50±0.051.59±0.04
  • BB+BNP decreased cellular susceptibility to arrhythmia by normalising Ca2+ homeostasis. Averaged Ca2+ transient amplitudes expressed as Indo1-AM fluorescence (F405/F480), averaged decay time constants (τ) of Ca2+ transients, averaged sarcoplasmic reticulum (SR)-Ca2+content following caffeine application, averaged diastolic Ca2+ levels, sarcomeres shortening (%) and percentage of cells exhibiting spontaneous irregular Ca2+ waves (n=50 cells, 5 mice/group). Ca2+ sparks. BB+BNP prevented Ca2+ leakage from RyR2. Averaged Ca2+ spark frequencies detected by Fluo4-AM fluorescence. Ca2+ sparks amplitude (variation of fluorescence at 505 nm/initial fluorescence at 505 nm, ΔF/F0), full width (FWHM) and full duration (FDHM) at half maximum of Ca2+ sparks (n=60 cells, 6 mice/group). *,†,‡ p<0.05, p<0.01, p<0.001 versus Sham; §,||,¶ p<0.05, p<0.01, p<0.001 versus PMI animals; # p<0.05 versus BB-PMI animals.

  • BB, β1-adrenergic blocker; BNP, B-type natriuretic peptide; PMI, postmyocardial infarction.