Table 1.
Vo and MLC isoforms of SM MHC type II fibers (MHC type IIB, IIX/IIB, IIX, IIAX)
| Group |
AC |
OC |
OE |
OM |
||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| MHCs |
||||||||||||||||
| Vo MLCs |
IIB | IIX/IIB | IIX | IIAX | IIB | IIX/IIB | IIX | IIAX | IIB | IIX/IIB | IIX | IIAX | IIB | IIX/IIB | IIX | IIAX |
| Vo (FL s−1) | 3.3 ± 0.2 | 3.2 ± 0.5 | 2.7 ± 0.0 | / | 2.5 ± 0.2a† | 2.3 ± 0.2a | 1.6 ± 0.3 | 2.4 ± 0.3 | 2.0 ± 0.2a† | 1.9 ± 0.2a | 1.7 ± 0.3† | 0.7 ± 0.3 | 3.6 ± 0.4 | 2.5 ± 0.3 | 2.9 ± 0.4 | 2.4 ± 0.0 |
| (40) | (6) | (1) | (14) | (15) | (5) | (6) | (8) | (22) | (11) | (2) | (14) | (17) | (9) | (1) | ||
| MLC1f (%) | 29.4 ± 1.5† | 26.4 ± 4.2† | 26.0 ± 0.0 | / | 51.6 ± 2.7a | 56.4 ± 2.4a | 50.0 ± 4.2 | 46.1 ± 5.1 | 48.8 ± 1.5a | 50.4 ± 3.1a | 42.3 ± 6.7 | 45.9 ± 10.8 | 47.7 ± 2.1a | 50.9 ± 2.4a | 46.1 ± 1.8 | 56.8 ± 0.0 |
| (48) | (4) | (1) | (28) | (49) | (6) | (13) | (8) | (22) | (11) | (2) | (14) | (17) | (9) | (1) | ||
| MLC2f (%) | 56.6 ± 1.7† | 62.0 ± 3.4† | 64.9 ± 0.0 | / | 44.5 ± 2.6a | 40.1 ± 2.3a | 45.4 ± 3.6 | 48.6 ± 4.6 | 45.2 ± 1.3a | 45.5 ± 2.8a | 52.1 ± 6.1 | 53.7 ± 10.8 | 43.7 ± 2.2a | 41.1 ± 2.4a | 46.8 ± 1.3 | 42.3 ± 0.0 |
| (48) | (4) | (1) | (28) | (49) | (6) | (13) | (8) | (22) | (11) | (2) | (14) | (17) | (9) | (1) | ||
| MLC3f (%) | 14.1 ± 0.9† | 11.6 ± 1.3 | 9.2 ± 0.0 | / | 3.9 ± 0.6a† | 3.5 ± 0.4a† | 4.6 ± 1.1 | 5.4 ± 0.9 | 6.0 ± 0.9a | 4.1 ± 0.5a† | 5.6 ± 0.9 | 0.4 ± 0.1 | 8.6 ± 1.1a | 8.0 ± 1.0 | 7.1 ± 1.6 | 1.0 ± 0.0 |
| (48) | (4) | (1) | (28) | (49) | (6) | (13) | (8) | (22) | (11) | (2) | (14) | (17) | (9) | (1) | ||
| MLC3F/2f (%) |
0.28 ± 0.03 | 0.19 ± 0.02 | 0.14 ± 0.00 | / | 0.09 ± 0.02a† | 0.09 ± 0.0 |a† | 0.10 ± 0.02 | 0.12 ± 0.02 | 0.13 ± 0.02a | 0.09 ± 0.0 |a† | 0.14 ± 0.03 | 0.01 ± 0.00 | 0.21 ± 0.03 | 0.21 ± 0.03 | 0.15 ± 0.04 | 0.02 ± 0.00 |
| (48) | (4) | (1) | (28) | (49) | (6) | (13) | (8) | (22) | (11) | (2) | (14) | (17) | (9) | (1) | ||
Vo and MLC isoforms in semimembranosus muscle (SM) myosin heavy chain (MHC) type II fibers were compared among groups: adult control (AC), old control (OC), old empty vector (OE), and old MLC3f (OM). The % MLC1f, % MLC2f, % MLC3f, and MLC3f/MLC2f ratio were determined from densitometric analysis of individual fibers.
a
indicates significantly different than AC.
†
indicates significantly different than OM. Values represent mean ± SEM. Significance was set at P < 0.05.