Table 2.
Cardiomyocytes Properties in L2Δ6 Mice
| WT | L2Δ6 | P Value | |
|---|---|---|---|
| Isolated myocytes* | |||
| Resting myocyte length (µm) | 1.75±0.06 | 1.76±0.05 | NS |
| % Sarcomere shortening | 6.6±2.1 | 7.4±2.8 | NS |
| Time to 50% contraction (mSec) | 25±7 | 65±15 | <0.001 |
| Time to 50% relaxation (mSec) | 148±40 | 310±80 | <0.001 |
| Ca2+ transient amplitude (Fura2 ratio) | 0.45±0.15 | 0.71±0.24 | <0.001 |
| Time to 50% transient decay (mSec) | 118±13 | 201±69 | <0.001 |
| Ca2+ transient decay–Tau (mSec) | 124±22 | 178±52 | <0.001 |
| Catecholamine stimulated myocytes † | |||
| Resting myocyte length (µm) | 1.72±0.06 | 1.73±0.06 | NS |
| % Sarcomere shortening | 12.9±3.3 | 13.5±3.7 | NS |
| Time to 50% contraction (mSec) | 20±4 | 32±13 | <0.05 |
| Time to 50% relaxation (mSec) | 107±18 | 150±50 | <0.05 |
| Ca2+ transient amplitude (Fura2 ratio) | 0.56±0.17 | 0.92±0.3 | <0.01 |
| Time to 50% transient decay (mSec) | 92±16 | 105±25 | NS |
| Ca2+ transient decay–Tau (mSec) | 68±9 | 69±17 | NS |
Data are expressed as mean±SEM. L2Δ6 indicates in‐frame LAMP2 gene exon 6 deletion; LAMP2, lysosome‐associated membrane protein‐2; NS, non‐significant; and WT, wild‐type.
*
Sarcomere lengths and shortening of myocytes (n=21 and n=29 cells from 4 wild‐type (WT) and 5 in‐frame LAMP2 exon 6 deletion (L2Δ6)mice, respectively). Ca2+ transients were measured in myocytes (n=30 cells and n=18) from 5 WT and 3 L2Δ6 mice, respectively.
†
Catecholamine‐stimulated sarcomere lengths and shortening were measured in myocytes (n=11 and n=10) from 4 WT and 3 L2Δ6 mice, respectively. Catecholamine‐stimulated Ca2+ transients were measured in myocytes (n=12 and n=12 cells from 4 WT and 3 L2Δ6 mice, respectively).