title: Possible link of different slow calcium signals generated by membrane potential and hormones to differential gene expression in cultured muscle cells.
abstract: The study of fluorescent calcium signals from cultured rat myotubes has provided interesting results in the past few years. Both K+ depolarization and tetanic electrical stimulation were shown to produce slow Ca2+ signals, unrelated to contraction and associated to regulation of gene expression in cultured rat myotubes. We studied the effect of IGF-I, insulin and testosterone on intracellular Ca2+ in cultured muscle cells. Insulin produced a fast (< 1 s) and transient [Ca2+] increase lasting less than 10 s. IGF-I induced a transient [Ca2+] increase, reaching a fluorescence peak 6 s after stimulus, to return to basal values after 60 s. Testosterone induced delayed (35 s) and long lasting (100-200 s) signals, frequently associated with oscillations. IGF-I, testosterone and electrical stimulation-induced Ca2+ signals were shown to be dependent on IP3 production. All of these Ca2+ signals were blocked by inhibitors of the IP3 pathway. On the other hand, insulin-induced Ca2+ increase was dependent on ryanodine receptors and blocked by either nifedipine or ryanodine. The different intracellular Ca2+ patterns produced by electrical stimulation, testosterone, IGF-I and insulin, may help to understand the role of intracellular calcium kinetics in the regulation of gene expression by various stimuli in skeletal muscle cells.
authors.affiliation: Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile. ejaimovi@med.uchile.cl
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
authors.forename: Alejandra
authors.initials: A
authors.lastname: Espinosa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D004558:Electric Stimulation; D015870:Gene Expression / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D032342:Muscle Cells / Q000187:drug effects* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D013739:Testosterone / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D007328:Insulin; D014157:Transcription Factors; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D002118:Calcium