Role of myoplasmic phosphate in contractile function of skeletal muscle: studies on creatine kinase‐deficient mice

• DOI: 10.1111/j.1469-7793.2001.0379a.x
• Publication Date: 2004-08-05T10:08:46Z
• Authors: Anders J. Dahlstedt; Abram Katz; Håkan Westerblad
• Keywords: Tetanic stimulation; Creatine kinase; Myofibril; Muscle relaxation

Increased myoplasmic inorganic phosphate (P i ) has been suggested to have an important role in skeletal muscle fatigue, especially the early phase. In present study we used intact fast‐twitch cells from mice completely deficient creatine kinase (CK ‐/‐ test this suggestion. These CK provide a good model since they display higher P concentration unfatigued state and fatigue without significant increase of . Tetanic contractions (350 ms duration) were produced single fibres. The free [Ca 2+ ] ([Ca was measured with fluorescent indicator indo‐1. force‐[Ca relationship constructed tetani at different frequencies. Compared wild‐type fibres, fibres displayed lower force 100 Hz saturating (i.e. stimulation during caffeine exposure), tetanic first stimulation, reduced myofibrillar Ca sensitivity when measurements performed 100–200 into tetani, slowed relaxation that due altered cross‐bridge kinetics rather than delayed removal myoplasm. series 10 resulted force, relaxation, increased amplitude tails after tetani. None these changes observed Complementary experiments on isolated extensor digitorum longus muscles showed reduction speed similar those conclusion, can explain phase fatigue. appears be involved both fatigue‐induced function SR handling.