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Caffeine administration results in greater tension development in previously fatigued canine muscle in situ
Author(s) -
Howlett Richard A.,
Kelley Kevin M.,
Grassi Bruno,
Gladden L. Bruce,
Hogan Michael C.
Publication year - 2005
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2005.031559
Subject(s) - isometric exercise , caffeine , chemistry , skeletal muscle , muscle contraction , contraction (grammar) , medicine , endocrinology , muscle fatigue , stimulation , electromyography , psychiatry
In isolated single skeletal myocytes undergoing long‐term fatiguing contractions, caffeine (CAF) can result in nearly immediate restoration of generated tension to near‐prefatigue levels by increasing Ca 2+ release via activation of sarcoplasmic reticulum release channels. This study tested whether arterial CAF infusion (>5 m m ) would cause a similar rapid restoration of tetanic isometric tension during contractions to fatigue in perfused canine hindlimb muscle in situ . Tetanic contractions were elicited by electrical stimulation (200 ms trains, 50 Hz, 1 contraction s −1 ), and biopsies were taken from the muscle at rest and during contractions: (1) following the onset of fatigue (tension ∼60% of initial value); and (2) following CAF administration. Resting muscle ATP, PCr and lactate contents were 25.2 ± 0.4, 76.9 ± 3.3 and 14.4 ± 3.3 mmol (kg dry weight) −1 , respectively. At fatigue, generated tetanic tension was 61.1 ± 6.9% of initial contractions. There was a small but statistically significant recovery of tetanic tension (64.9 ± 6.6% of initial value) with CAF infusion, after which the muscle showed incomplete relaxation. At fatigue, muscle ATP and PCr contents had fallen significantly ( P < 0.05) to 18.1 ± 1.1 and 18.9 ± 2.1 mmol (kg dry weight) −1 , respectively, and lactate content had increased significantly to 27.7 ± 5.4 mmol (kg dry weight) −1 . Following CAF, skeletal muscle ATP and PCr contents were significantly lower than corresponding fatigue values (15.0 ± 1.3 and 10.9 ± 2.2 mmol (kg dry weight) −1 , respectively), while lactate was unchanged (22.2 ± 3.9 mmol (kg dry weight) −1 ). These results demonstrate that caffeine can result in a small, but statistically significant, recovery of isometric tension in fatigued canine hindlimb muscle in situ , although not nearly to the same degree as seen in isolated single muscle fibres. This suggests that, in this in situ isolated whole muscle model, alteration of Ca 2+ metabolism is probably only one cause of fatigue.