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Tension responses to quick length changes of glycerinated skeletal muscle fibres from the frog and tortoise
Author(s) -
Heinl P.,
Kuhn H. J.,
Rüegg J. C.
Publication year - 1974
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1974.sp010480
Subject(s) - isometric exercise , sarcomere , tension (geology) , anatomy , tortoise , chemistry , biophysics , materials science , biology , myocyte , composite material , ultimate tensile strength , zoology , physiology , endocrinology
1. Twitch fibres isolated from the sartorius muscle of the frog were glycerinated (cf. Heinl, 1972) and thin fibre bundles dissected from the m. ileofibularis of the tortoise were briefly glycerinated as described by Julian (1971). 2. The glycerinated fibres (length 0·3–0·5 cm) were fixed to an apparatus which performed length changes within 5 msec and recorded the time course of tension changes in the fibres. 3. The fibres were suspended in a relaxing medium, containing ATP and 4 m M ‐EGTA. Contraction was induced by raising the calcium concentration to 4 m M ‐CaEGTA. 4. The tension time course of activated fibres following quick length changes (0·1–1% L 0 ) was studied. The tension records produced by quick releases and stretches could be resolved into four phases similar to the kind shown in Fig. 1 a . 5. The phase of quick tension recovery was found to take place more rapidly in frog than in tortoise fibres: it was completed in ∼ 30 msec (after stretch) and in ∼ 20 msec (after release) in frog fibres (3° C). The corresponding values obtained for tortoise fibres were ∼ 300 and ∼ 400 msec (3° C). 6. In tortoise fibres the size of the elastic and quick recovery phase increased with rising isometric tension (induced by raising the calcium concentration (pCa 8 to 5)), and decreased with increasing sarcomere length (2·5–4·2 μm). In fibres, in which the rigor state was induced by withdrawal of ATP, no quick tension recovery was recorded. 7. It is suggested that the rotational movement of the crossbridge head on the actin filament, postulated by Huxley & Simmons (1971 b ) is taking place more slowly in the tortoise than in the frog muscle. Furthermore, it is suggested that this rotational movement does not occur in the rigor state, as no quick tension recovery was recorded there.