Magnesium in muscle fibre types - myofibrillar contraction

Research project P 14753 Magnesium in muscle fibre types - myofibrillar contraction Stefan GALLER 09.10.2000 The specific physiological role of intracellular magnesium (Mg2+) is only partially known both on the cellular and on the molecular level. The relatively high concentration of this ion and its ability to affect intracellular proteins suggest a great physiological importance both in healthy and diseased tissue. The most important known function of Mg2+ is to bind to ATP, building up a complex which is the energy source for cellular processes. Among all body cells, striated muscle cells possess important advantages for studying the cellular function of intracellular Mg2+. These advantages include the possibility to measure intracellular functions (i.e. force and movement) with high resolution. Furthermore, Mg2+ effects are already known on the level of whole body muscle physiology. This is a good indicator that effects will also be seen at the cellular level. Single muscle fibres provide a good model for exploring the functional role of this "forgotten cation" (Brady et al. 1987). In the present project the effects of Mg2+ on various contractile properties of intracellular force-generating structures (=myofibrils) originating from defined muscle fibre types will be investigated. A part of the studies will be carried out on demernbranated (=skinned) muscle fibres, the other part on intact fibres. In addition, measurements of intracellular free Mg2+ concentration will be carried out on intact fibres under various experimental conditions. All fibres used in physiological experiments will be biochemically analysed for investigating the isoforms of their myofibrillar proteins. Using this analysis it may be possible to relate the Mg2+ effects to specific proteins. It will also allow the study of the physiological role of Mg2+ in fibre types with different functional demands. In order to maximise chances for success in this project it is very important to use differen muscle preparations. There are several reasons for this: Certain experimental results are best achieved in particular preparations. The literature available on certain aspects of contractility differs from preparation to preparation. We are planning to use skeletal muscle fibres from mammalian and crustaceans. It is expected that the results of the project will lead to a better understanding of the specific physiologiqal and molecular roles of intracellular Mg2+. Some preliminary results make our project very promising.