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The effect of sarcomere non‐uniformity on the sarcomere length‐tension relationship of skinned fibers
Author(s) -
Iwazumi Tatsuo,
Pollack Gerald H.
Publication year - 1981
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041060302
Subject(s) - sarcomere , isometric exercise , contraction (grammar) , biophysics , tension (geology) , chemistry , anatomy , myofibril , fiber , muscle fibre , muscle contraction , materials science , biomedical engineering , myocyte , skeletal muscle , ultimate tensile strength , composite material , biology , medicine , biochemistry , microbiology and biotechnology , endocrinology
It has proved difficult to activate skinned muscle fibers to produce high tension (3 kg/cm 2 level) without loss of clear striations. A new method was developed which permits high tension production in skinned muscle fibers while retaining clear striations. Clear striations allow reliable measurement of the sarcomere lengths during contraction by microscopy and diffractometry. The method is to increase the Ca ++ concentration of the bathing solution very gradually over a time period of 5 to 10 minutes. Once the skinned fiber is conditioned by this slow activation, subsequent contractions can be elicited by ordinary quick activations without loss of striations. When the experiments are carried out with careful controls for the uniformity of the sarcomere length distribution along the entire length of the fiber, contractions are highly repeatable. Using the new method and stringent quality control of fibers, the sarcomere length‐isometric tension relationship of skinned rabbit soleus fibers was obtained. The results differ from those previously obtained by conventional activation methods in that tension increases with sarcomere length not only at low (pCa = 5.8), but also at high (pCa = 5.2), calcium concentration.