Effect of electrical stimulation on total contents of K+ and Na+ in isolated rat EDL muscle in vitro
| Experimental conditions | Total K+ content | Total Na+ content |
| µmol/g wet wt | µmol/g wet wt | |
| Resting muscles | 103.7 ± 2.1 (9) | 13.6 ± 1.0 (9) |
| 5-Hz stimulation, 300 s | 98.2 ± 0.9 (9)a | 18.2 ± 0.6 (9)b |
| Resting muscles | 102.8 ± 1.9 (5) | 11.8 ± 0.6 (5) |
| 60-Hz stimulation, 60 s | 92.8 ± 1.9 (5)c | 21.6 ± 0.4 (5)d |
| Experimental conditions | Total K+ content | Total Na+ content |
| µmol/g wet wt | µmol/g wet wt | |
| Resting muscles | 103.7 ± 2.1 (9) | 13.6 ± 1.0 (9) |
| 5-Hz stimulation, 300 s | 98.2 ± 0.9 (9)a | 18.2 ± 0.6 (9)b |
| Resting muscles | 102.8 ± 1.9 (5) | 11.8 ± 0.6 (5) |
| 60-Hz stimulation, 60 s | 92.8 ± 1.9 (5)c | 21.6 ± 0.4 (5)d |
The muscles were mounted in force transducers for measurement of isometric contractions, adjusted to optimal length, and equilibrated for 30 min in KR buffer at 30°C during gassing with a mixture of 95% O2 and 5% CO2. Continuous direct stimulation was performed using 10-V, 1-ms pulses at 5 or 60 Hz. After stimulation, all muscles were immediately washed four times for 15 min in ice-cold Na+-free Tris-sucrose buffer, blotted, weighed, and taken for flame photometric determination of Na+ and K+ contents. The contralateral muscles from the same animals were allowed to rest, and their content of Na+ and K+ was compared with that of the stimulated muscles. All values are given as means ± SEM, with the number of muscles in parentheses.
P < 0.03 compared with resting muscles.
P < 0.002 compared with resting muscles.
P < 0.006 compared with resting muscles.
P < 0.001 compared with resting muscles.