Muscle Cell Physiology
Signal transduction leading to skeletal muscle adaptation to exercise is being studied by a group of laboratories under the leadership of Enrique Jaimovich; his own laboratory is specialized in measurement of calcium mediated signals in cultured muscle cells, include as associated scientists Jorge Hidalgo, doing research in the electrophysiological aspects of these signals and Manuel Estrada molecular aspects of hormone-related signals. Associated laboratories include that of Nora Riveros in muscle gene expression. Post doctoral trainees include Sonja Buvinic, Mariana Casas, Alejandra Espinosa and Nevenka Juretic. In skeletal muscle, increased use, disuse and fiber damage are known to trigger adaptive processes. Cellular mechanisms involved in these adaptive processes are nevertheless poorly known. The process of muscle adaptation is controlled by nerve activity and by nerve-muscle interaction; it constitutes therefore a model for both plasticity and regeneration of excitable tissues. Calcium ions act as intracellular messengers associated to regulation of gene expression in a variety of cell types. Nevertheless, due to its mayor role in muscle contraction, its role in the regulation of other processes has not been studied in detail. Our group has described that in cultured myotubes, calcium transients evoked by membrane depolarization can be modeled by two processes that are independent in terms of their pharmacology, kinetics and cellular location. Only the early component is associated to contraction; the delayed component, lasting several seconds, represents a different type of signal and can be associated to intracellular signaling cascades involved in the regulation of gene expression.