TABLE 4.
Summary of Ca2+ and contractile transient parameters measured from cardiomyocytes isolated from old WT and R21C KI mice
*, p < 0.05 versus WT; †, p < 0.01 versus WT.
| Parameter | WTa |
R21Ca |
||||||
|---|---|---|---|---|---|---|---|---|
| 0.5 Hz | 2.0 Hz | 3.0 Hz | 4.0 Hz | 0.5 Hz | 2.0 Hz | 3.0 Hz | 4.0 Hz | |
| −ISOb | ||||||||
| [Ca2+]i decay (t½) (ms)c | 175 ± 4 | 139 ± 3 | 126 ± 2 | 119 ± 2 | 177 ± 6 | 142 ± 4 | 129 ± 4 | 121 ± 3 |
| Diastolic [Ca2+]i (Fura-2 ratio)d | 0.51 ± 0.01 | 0.51 ± 0.01 | 0.52 ± 0.01 | 0.52 ± 0.01 | 0.54 ± 0.02 | 0.54 ± 0.02 | 0.54 ± 0.02 | 0.55 ± 0.03 |
| Time to peak [Ca2+]i (ms)e | 51.6 ± 3.1 | 45.7 ± 2.6 | 44.5 ± 2.3 | 44.7 ± 2.4 | 62.0 ± 2.6* | 53.8 ± 2.3* | 49.2 ± 2.9 | 49.1 ± 2.4 |
| Systolic [Ca2+]i (Fura-2 ratio)d | 0.58 ± 0.01 | 0.58 ± 0.02 | 0.58 ± 0.02 | 0.58 ± 0.02 | 0.60 ± 0.02 | 0.60 ± 0.02 | 0.60 ± 0.02 | 0.60 ± 0.02 |
| Ca2+ amplitude (%)f | 14.2 ± 1.4 | 14.4 ± 1.3 | 13.8 ± 1.4 | 13.9 ± 1.4 | 8.8 ± 0.5† | 9.7 ± 0.1† | 9.9 ± 1.0* | 9.3 ± 0.9* |
| SL relaxation (t½) (ms)c | 51.0 ± 3.4 | 41.0 ± 2.3 | 36.8 ± 2.2 | 32.4 ± 1.8 | 64.0 ± 3.3* | 52.4 ± 3.2† | 44.8 ± 2.2* | 38.7 ± 2.4* |
| Diastolic SL (μm) | 1.76 ± 0.01 | 1.75 ± 0.01 | 1.74 ± 0.02 | 1.74 ± 0.02 | 1.75 ± 0.03 | 1.73 ± 0.01 | 1.72 ± 0.01 | 1.72 ± 0.02 |
| Time to peak shortening (ms)e | 99.7 ± 4.7 | 83.0 ± 2.8 | 76.9 ± 2.9 | 73.1 ± 2.3 | 116.6 ± 4.7* | 92.8 ± 3.4* | 86.6 ± 3.3* | 79.2 ± 2.7 |
| SL amplitude (%)f | 10.8 ± 1.0 | 10.5 ± 0.8 | 10.3 ± 0.8 | 10.0 ± 0.7 | 9.9 ± 0.61 | 9.2 ± 1.0 | 8.9 ± 1.0 | 9.3 ± 1.0 |
| +ISOb | ||||||||
| [Ca2+]i decay (t½) (ms)c | 123 ± 2 | 104 ± 2 | 98 ± 2 | 96 ± 1 | 139 ± 3† | 113 ± 2† | 106 ± 2* | 103 ± 2* |
| Diastolic [Ca2+]i (Fura-2 ratio)d | 0.46 ± 0.01 | 0.47 ± 0.01 | 0.48 ± 0.01 | 0.49 ± 0.01 | 0.53 ± 0.02† | 0.53 ± 0.02† | 0.53 ± 0.02* | 0.53 ± 0.02* |
| Time to peak [Ca2+]i (ms)e | 34.9 ± 2.5 | 30.6 ± 2.0 | 30.6 ± 2.2 | 30.1 ± 2.3 | 46.4 ± 4.2* | 41.1 ± 2.7† | 38.7 ± 2.5* | 37.4 ± 2.7 |
| Systolic [Ca2+]i (Fura-2 ratio)d | 0.62 ± 0.02 | 0.63 ± 0.02 | 0.64 ± 0.03 | 0.66 ± 0.03 | 0.60 ± 0.02 | 0.59 ± 0.02 | 0.59 ± 0.02 | 0.60 ± 0.02 |
| Ca2+ amplitude (%)f | 31.2 ± 4.0 | 29.3 ± 3.6 | 29.7 ± 3.6 | 28.9 ± 3.3 | 12.6 ± 0.9† | 12.8 ± 0.8† | 13.5 ± 0.9† | 14.0 ± 0.9† |
| SL relaxation (t½) (ms)c | 43.2 ± 2.7 | 36.5 ± 2.6 | 33.8 ± 2.3 | 31.6 ± 2.3 | 52.7 ± 3.3* | 45.0 ± 2.6* | 42.6 ± 1.7† | 41.1 ± 1.9† |
| Diastolic SL (μm) | 1.75 ± 0.01 | 1.73 ± 0.01 | 1.72 ± 0.01 | 1.69 ± 0.02 | 1.74 ± 0.01 | 1.72 ± 0.01 | 1.70 ± 0.01 | 1.67 ± 0.01 |
| Time to peak shortening (ms)e | 82.3 ± 3.4 | 71.7 ± 1.8 | 67.9 ± 1.5 | 67.8 ± 1.9 | 94.2 ± 4.1* | 81.1 ± 2.5† | 76.7 ± 2.2† | 72.6 ± 2.0 |
| SL amplitude (%)f | 14.5 ± 1.0 | 13.9 ± 0.9 | 14.6 ± 0.9 | 14.7 ± 0.9 | 14.9 ± 0.8 | 13.8 ± 0.6 | 13.8 ± 0.7 | 13.7 ± 0.6 |
a Values are given as mean ± S.E. (measurements were taken from 3 WT and 3 R21C KI mice (15 months old); 4–6 cells/heart were studied).
b +ISO and −ISO, presence and absence of 100 nmol/liter isoproterenol, respectively.
c t½, time it takes for the Ca2+ and SL amplitudes to decrease by 50%.
d Fura-2 was excited at 340 and 380 nm, and the ratio of their emissions at 510 nm (i.e. Fura-2 ratio) represents the [Ca2+]i.
e Time to peak, time it takes for the [Ca2+]i and SL at diastole to reach the peak [Ca2+]i and SL shortening at the end of systole.
f Ca2+ and SL amplitude, percentage increase of [Ca2+]i and SL shortening that occurs during systole and is calculated using the equation, (|x − y|/y) × 100, where x is the peak systolic Fura-2 ratio (or SL), and y is the diastolic Fura-2 ratio (or SL).