title: Direct in vivo monitoring of sarcoplasmic reticulum Ca2+ and cytosolic cAMP dynamics in mouse skeletal muscle.
abstract: Skeletal muscle contraction depends on the release of Ca(2+) from the sarcoplasmic reticulum (SR), but the dynamics of the SR free Ca(2+) concentration ([Ca(2+)](SR)), its modulation by physiological stimuli such as catecholamines, and the concomitant changes in cAMP handling have never been directly determined. We used two-photon microscopy imaging of GFP-based probes expressed in mouse skeletal muscles to monitor, for the first time in a live animal, the dynamics of [Ca(2+)](SR) and cAMP. Our data, which were obtained in highly physiological conditions, suggest that free [Ca(2+)](SR) decreases by approximately 50 microM during single twitches elicited through nerve stimulation. We also demonstrate that cAMP levels rise upon beta-adrenergic stimulation, leading to an increased efficacy of the Ca(2+) release/reuptake cycle during motor nerve stimulation.
authors.affiliation: Department of Biomedical Sciences, University of Padua, I-35121 Padua, Italy. rudiger.rudolf@itg.fzk.de
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Rudolf
authors.forename: Paulo J
authors.initials: PJ
authors.lastname: Magalhães
authors.forename: Tullio
authors.initials: T
authors.lastname: Pozzan
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D007211:Indoles / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases
chemical_list: D002135:Calcium-Binding Proteins; D007211:Indoles; D008164:Luminescent Proteins; C503159:cameleon YC6.1; D000242:Cyclic AMP; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid