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Response of ventilatory muscles of the rat to endurance training (1982)

Moore, Russell L. ; Gollnick, Philip D.

Springer

Pflügers Archiv 392 (1982), S. 268-271

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ISSN: 1432-2013

Keywords: Succinate dehydrogenase ; Training and ventilatory muscles ; Phosphorylase ; Hexokinase ; Lactate dehydrogenase ; Diaphragm ; Intercostal muscles ; Glycogen depletion

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract The effect of endurance training on the oxidative and glycolytic potentials of the diaphragm and intercostal muscles of rats has been studied. Training consisted of treadmill running (28 m/min, 60 min/day, 5 days/wk) for periods ranging from 8–26 weeks. Exercise of similar duration and intensity produced a glycogen depletion in the diaphragm and intercostal muscles of nontrained rats. Oxidative potential was estimated from the activity of the mitochondrial marker enzyme succinate dehydrogenase (SDH). The activities of phosphorylase (PHOS), hexokinase (HK), and lactate dehydrogenase (LDH) were determined as well as the distribution of the LDH isozymes. SDH activity averaged 44 (42–51) and 17 (10–22)% (P〈0.01) greater in the plantaris and diaphragm muscles, respectively, after 8–12 weeks of endurance running as compared to the sedentary animals. There was no change in the SDH activity of the intercostal muscles or in the activities of the glycolytic enzymes. There was also no change in the distribution of the isozymes of LDH. Extending the duration of the training program to 26 weeks did not produce any additional alteration in the magnitude of the adaptation observed after the initial training period. Comparative studies of different types of muscles demonstrated that the diaphragm, although having a fiber composition somewhat similar to that of a fast-twitch skeletal muscle, has a metabolic profile that is intermediate between pure slow twitch skeletal muscle and cardiac muscle.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00584308

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Phosphorylation of rabbit skeletal muscle myosin in situ (1985)

Moore, Russell L. ; Houston, Michael E. ; Stull, James T. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 125 (1985), S. 301-305

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ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Myosin light chain (P light chain) is phosphorylated by Ca2+. calmodulindependent myosin light chain kinase. Based on studies with rat skeletal muscles, it has been shown that P light chain phosphorylation correlated to the extent of potentiation of isometric twitch tension. It is not clear whether this correlation exists in rabbit skeletal muscle, which has been the primary source of contractile proteins for biochemical studies. Therefore, phosphorylation of myosin P light chain in rabbit slow-twitch soleus and fast-twitch plantaris muscles in situ was examined. Electrical stimulation (5 Hz, 20 seconds) of plantaris muscle produced an increase in the phosphate content of P light chain from 0.17 to 0.45 mol phosphate/mol P light chain. This increase in phosphate content was accompanied by a 58% increase in maximal isometric twitch tension. Tetanic stimulation (100 Hz, 15 seconds) of rabbit soleus muscle resulted in only a small increase in P light chain phosphate content from 0.02 to 0.10 mol phosphate/mol P light chain, and posttetanic twitch tension did not increase significantly. The correlation between potentiated isometric twitch tension and P light chain phosphorylation in rabbit fast-twitch muscle is similar to that observed in rat skeletal muscle. These results were consistent with the hypothesis that phosphorylation of rabbit skeletal muscle myosin, which results in an increase in actin-activated ATPase activity, may be related to isometric twitch potentiation.

Additional Material: 1 Ill.