Fatigue and metabolism of frog muscle fibers during stimulation and in response to caffeine
| Autor: | S I Rapoport, J V Passonneau, V Nassar-Gentina |
|---|---|
| Rok vydání: | 1981 |
| Předmět: |
Male
medicine.medical_specialty Contraction (grammar) Phosphocreatine Physiology Potassium chemistry.chemical_element Stimulation Sarcomere Potassium Chloride chemistry.chemical_compound Adenosine Triphosphate Caffeine Internal medicine medicine Animals Lactic Acid Muscles Rana pipiens Cell Biology Metabolism Adenosine Electric Stimulation Endocrinology Biochemistry chemistry Lactates Female Glycogen Muscle Contraction medicine.drug |
| Zdroj: | American Journal of Physiology-Cell Physiology. 241:C160-C166 |
| ISSN: | 1522-1563 0363-6143 |
| DOI: | 10.1152/ajpcell.1981.241.3.c160 |
| Popis: | Tension and metabolite concentrations were measured in single frog muscle fibers at 15 degrees C in vitro, in response to electrical stimulation or to immersion in caffeine- or potassium chloride-Ringer. Sarcomere length equaled 2.3 micrometers. Interrupted stimulation for 150 s at 20 Hz or stimulation for 7.5 min at 1 Hz was followed by at least 20 min of fatigue, evidenced by a reduced 200-ms test contraction. Fatigued fibers contracted maximally in potassium chloride- or caffeine-Ringer. They had high lactate and glucose 6-phosphate concentrations and a reduced phosphocreatine (PCr) concentration. Adenosine 5'-triphosphate (ATP) concentration was approximately normal but was markedly reduced by a caffeine contracture. A plot of PCr consumption against the tension-time integral at different stimulation frequencies (25, 35, or 50 Hz) and durations had an intercept of 25.5 nmol PCr/mg protein at time zero and a corrected slope of 0.65 nmol approximately P/mg protein per kg . s . cm-2. Prolonged fatigue is not due to energy exhaustion or to the inability of muscle fibers to consume residual ATP but probably arises from long-lasting interference in excitation-contraction coupling, which can be reversed by KCl- or caffeine-induced release of Ca2+ from intracellular stores. |
| Databáze: | OpenAIRE |
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