title: Intracellular calcium movements in skinned muscle fibres.
abstract: 1. Force development and (45)Ca movement between the internal membranes and the myofilament space were measured in segments of skinned muscle fibres.2. At 20 degrees C calcium ions in the myofilament space of calcium loaded fibres caused the internal membranes to release a substantial amount of calcium which produced a large force spike. Calcium produced a similar force spike in fibres containing only the physiological level of calcium when the temperature was lowered to about 6 degrees C.3. The force spike at 6 degrees C was inhibited when the magnesium concentration in the bathing solution was increased from 1 to 6 mM. The pattern of force development in preparations transferred directly from oil to a free calcium solution indicated that the normal concentration of Mg(2+) in the myofilament space of intact fibres is of the order of 10(-3)M.4. A possible role for the regenerative calcium release mechanism in the physiological activation of muscle fibres is suggested.
mesh_terms: D000200:Action Potentials; D000818:Animals; D001001:Anura; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002127:Calcium Isotopes; D066298:In Vitro Techniques; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D008566:Membranes / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009210:Myofibrils / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013696:Temperature
chemical_list: D002127:Calcium Isotopes; D008274:Magnesium; D002118:Calcium