TABLE 3.
Summary of Ca2+ and contractile transient parameters measured from cardiomyocytes isolated from young 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 | 124 ± 12 | 89 ± 4 | 79 ± 5 | 64 ± 2 | 122 ± 4 | 86 ± 1 | 76 ± 2 | 66 ± 2 |
| Diastolic [Ca2+]i (Fura-2 ratio)d | 0.49 ± 0.02 | 0.51 ± 0.02 | 0.52 ± 0.02 | 0.53 ± 0.02 | 0.52 ± 0.01 | 0.53 ± 0.01 | 0.53 ± 0.001 | 0.54 ± 0.01 |
| Ca2+ amplitude (%)e | 19.9 ± 2.8 | 18.6 ± 2.7 | 19.4 ± 2.5 | 20.0 ± 2.5 | 14.2 ± 1.2* | 15.5 ± 1.2 | 16.2 ± 1.23 | 16.5 ± 1.0 |
| SL relaxation (t½) (ms)c | 58 ± 6 | 48 ± 4 | 46 ± 4 | 39 ± 3 | 64 ± 3 | 48 ± 2 | 45 ± 2 | 43 ± 2 |
| Diastolic SL (μm) | 1.75 ± 0.02 | 1.71 ± 0.02 | 1.69 ± 0.02 | 1.68 ± 0.03 | 1.73 ± 0.01 | 1.71 ± 0.01 | 1.69 ± 0.01 | 1.67 ± 0.02 |
| SL amplitude (%)e | 12.4 ± 0.8 | 10.6 ± 0.6 | 10.8 ± 0.6 | 9.9 ± 0.6 | 11.8 ± 0.8 | 10.9 ± 0.7 | 9.8 ± 0.9 | 9.2 ± 9 |
| +ISOb | ||||||||
| [Ca2+]a decay (t½) (ms)c | 72 ± 3 | 57 ± 2 | 55 ± 1 | 52 ± 2 | 76 ± 2 | 58 ± 1 | 56 ± 1 | 53 ± 1 |
| Diastolic [Ca2+]i (Fura-2 ratio)d | 0.53 ± 0.01 | 0.57 ± 0.02 | 0.57 ± 0.02 | 0.58 ± 0.02 | 0.51 ± 0.01 | 0.52 ± 0.01† | 0.52 ± 0.01* | 0.54 ± 0.02* |
| Ca2+ amplitude (%)e | 26.2 ± 3.5 | 27.0 ± 3.6 | 28.8 ± 4.1 | 28.6 ± 3.8 | 16.0 ± 1.2† | 16.2 ± 0.9† | 16.8 ± 1.1† | 18.3 ± 0.9† |
| SL relaxation (t½) (ms)c | 48 ± 4 | 41 ± 2 | 41 ± 3 | 41 ± 3 | 50 ± 2 | 41 ± 2 | 39 ± 1 | 37 ± 1 |
| Diastolic SL (μm) | 1.76 ± 0.02 | 1.72 ± 0.02 | 1.71 ± 0.02 | 1.67 ± 0.02 | 1.76 ± 0.01 | 1.73 ± 0.02 | 1.71 ± 0.02 | 1.69 ± 0.02 |
| SL amplitude (%)e | 15.7 ± 1.0 | 15.1 ± 0.9 | 15.2 ± 1.1 | 15.0 ± 1.0 | 15.6 ± 0.9 | 15.2 ± 0.9 | 14.8 ± 0.9 | 14.1 ± 0.9 |
a Values are given as mean ± S.E. (measurements were taken from 3 WT and 3 R21C KI mice (6 months old); 3–4 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 Ca2+ and SL amplitude represents the 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).