Intracellular Ca2+ at rest and during stimulation in mouse lumbrical muscles at 37°C
| Dye and parameter | Time pre-PS | Time post-PS | |
| Furaptra | −60 s | 5.0 s | 20 s |
| Amplitude (Ratio units) | 0.0131 ± 0.0007 | 0.0127 ± 0.0007 | 0.0132 ± 0.0007 |
| Time to peak (ms) | 1.8 ± 0.1 | 1.8 ± 0.1 | 1.8 ± 0.1 |
| ICT 50% decay time (ms) | 3.1 ± 0.6 | 2.7 ± 0.4 | 2.8 ± 0.4 |
| FWHM (ms) | 3.6 ± 0.5 | 3.7 ± 0.4 | 3.7 ± 0.4 |
| Fura-2 | −30 s | 2.5 s | 30 s |
| Resting Ca2+ (Ratio units) | 0.376 ± 0.017 | 0.418 ± 0.022a | 0.395 ± 0.019b |
| Dye and parameter | Time pre-PS | Time post-PS | |
| Furaptra | −60 s | 5.0 s | 20 s |
| Amplitude (Ratio units) | 0.0131 ± 0.0007 | 0.0127 ± 0.0007 | 0.0132 ± 0.0007 |
| Time to peak (ms) | 1.8 ± 0.1 | 1.8 ± 0.1 | 1.8 ± 0.1 |
| ICT 50% decay time (ms) | 3.1 ± 0.6 | 2.7 ± 0.4 | 2.8 ± 0.4 |
| FWHM (ms) | 3.6 ± 0.5 | 3.7 ± 0.4 | 3.7 ± 0.4 |
| Fura-2 | −30 s | 2.5 s | 30 s |
| Resting Ca2+ (Ratio units) | 0.376 ± 0.017 | 0.418 ± 0.022a | 0.395 ± 0.019b |
All data are presented as mean ± SEM (n = 10 furaptra or n = 9 fura-2). Fura-2 data reported for 2.5 and 30 s correspond to peak twitch force potentiation and the first return of peak twitch force to unpotentiated levels after PS, respectively. Furaptra signals during twitch contractions were averages of those occurring 90, 60, and 30 s before the onset of the PS (denoted as −60 s), 2.5, 5.0, and 7.5 s after the end of the PS (denoted as 5.0 s) and 10, 20, and 30 s after the end of the PS (denoted as 20 s) for each muscle. PS, potentiating stimulus (20 Hz for 2.5 s at optimum length for twitch tension (Lo)); ICT, intracellular Ca2+ transient; FWHM, full width at half-maximum.
Post-PS value at 2.5 s significantly different than pre-PS value (P < 0.001).
Post-PS value at 30 s is significantly different than pre-PS value (P < 0.01) and post-PS value at 2.5 s (P < 0.01).