Effects of elevated [K+]o on 36Cl uptake in isolated rat EDL muscle in vitro
| Buffer composition | 36Cl uptake | Intracellular 36Cl | Relative increase | P-values |
| µmol/g wet wt | mM | % | ||
| KR with 4 mM K+ | 8.8 ± 1.3 (5) | 17.3 ± 2.5 (5) | ||
| KR with 40 mM K+ | 19.4 ± 3.0 (5) | 38.0 ± 5.9 (5) | 120 | 0.011 |
| KR with 60 mM K+ | 29.7 ± 1.1 (3) | 58.2 ± 2.2 (3) | 238 | <0.001 |
| KR with 80 mM K+ | 43.9 ± 2.3 (3) | 86.1 ± 4.5 (3) | 399 | <0.001 |
| Buffer composition | 36Cl uptake | Intracellular 36Cl | Relative increase | P-values |
| µmol/g wet wt | mM | % | ||
| KR with 4 mM K+ | 8.8 ± 1.3 (5) | 17.3 ± 2.5 (5) | ||
| KR with 40 mM K+ | 19.4 ± 3.0 (5) | 38.0 ± 5.9 (5) | 120 | 0.011 |
| KR with 60 mM K+ | 29.7 ± 1.1 (3) | 58.2 ± 2.2 (3) | 238 | <0.001 |
| KR with 80 mM K+ | 43.9 ± 2.3 (3) | 86.1 ± 4.5 (3) | 399 | <0.001 |
The muscles were mounted in force transducers for measurement of isometric contractions, adjusted to optimal length, and equilibrated for 15 min in KR buffer at 30°C during gassing with a mixture of 95% O2 and 5% CO2. Then the muscles were incubated for 90 min in KR buffer in which NaCl had been replaced by KCl at the concentrations indicated and 0.4 µCi/ml 36Cl added. All muscles were washed four times for 15 min in Na+-free Tris-sucrose buffer to remove extracellular tracer, blotted, weighed, and taken for scintillation counting of 36Cl. For each muscle, the content of 36Cl was measured and expressed as µmol/g wet wt using the specific activity of 36Cl in the loading medium. The data were corrected for the loss of 36Cl during the washout and are given as µmol/g wet wt ± SEM, with the number of muscles in parentheses.