Ramírez BU, Soza MA. Intramuscular pH and endurance are abnormal in skeletal muscles from rats with experimental myotonia.
Exp Neurol 1988;
101:347-55. [PMID:
3416978 DOI:
10.1016/0014-4886(88)90046-5]
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Abstract
The relation between resistance to fatigue and intramuscular pH was studied in fast muscles (anterior tibialis and extensor digitorum longus) from rats treated with 2,4-dichlorophenoxyacetic acid (2,4-D) to induce myotonia. Fatiguability was studied in muscles indirectly stimulated at 30 Hz (330 ms/s; 1 train/s) for 2 min. The resistance to fatigue decreased significantly 1 h after drug treatment and remained low 24 h later. The intramuscular pH was lower than normal in resting muscles from 2,4-D-treated rats. After 2 min of stimulation the pH decreased in both control and drug-treated muscles. However, this decrement was reduced in the experimental muscles. The pH of control and of 2,4-D-treated muscles were similar after the stimulation period, but only the drug-treated muscles were fatigued. Therefore, a decrease in intramuscular pH would not be the cause of the observed decrease in muscle resistance to fatigue after 2,4-D treatment. The reduced endurance of drug-treated muscles could not be attributed to impaired neuromuscular transmission.
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