Localization of the site of Ca2 + release at the level of a single sarcomere in skeletal muscle fibres

• DOI: 10.1038/367739a0
• Publication Date: 2003-08-12T18:48:29Z
• Authors: Ariel L. Escobar; Jonathan R. Monck; Julio M. Fernandez; Julio L. Vergara
• Keywords: Sarcomeres; Microscopy; 0303 health sciences; 03 medical and health sciences; Rana catesbeiana; Lasers; Muscles; Action Potentials; Animals; Calcium; Fluorescence

The development of mechanical force in skeletal muscle fibres is brought about by rapid increases in the intracellular calcium concentration (Ca2+ transients) which can be detected by optical methods. Local stimulation experiments and ultrastructural evidence suggest that, at a microscopic level, these Ca2+ transients are generated by the release of Ca2+ ions from the terminal cisternae of the sarcoplasmic reticulum in response to the depolarization of the transverse tubules (t-tubules). Nevertheless, to date, there is no functional information on the exact location at which Ca2+ release takes place. The present experiments were designed to obtain direct evidence about dynamic changes in localization and microscopic distribution of Ca2+ in a single sarcomere using two independent novel methodologies: confocal spot detection of Ca2+ transients and Ca2+ imaging with pulsed laser excitation.