In vivo monitoring of Ca(2+) uptake into mitochondria of mouse skeletal muscle during contraction.
Although the importance of mitochondria in patho-physiology has become increasingly evident, it remains unclear whether these organelles play a role in Ca(2+) handling by skeletal muscle. This undefined situation is mainly due to technical limitations in measuring Ca(2+) transients reliably during the contraction-relaxation cycle. Using two-photon microscopy and genetically expressed "cameleon" Ca(2+) sensors, we developed a robust system that enables the measurement of both cytoplasmic and mitochondrial Ca(2+) transients in vivo. We show here for the first time that, in vivo and under highly physiological conditions, mitochondria in mammalian skeletal muscle take up Ca(2+) during contraction induced by motor nerve stimulation and rapidly release it during relaxation. The mitochondrial Ca(2+) increase is delayed by a few milliseconds compared with the cytosolic Ca(2+) rise and occurs both during a single twitch and upon tetanic contraction.
Department of Biomedical Sciences, Institute of Neurosciences, University of Padua, Viale G. Colombo 3, I-35121 Padua, Italy.
Rüdiger
R
Rudolf
Marco
M
Mongillo
Paulo J
PJ
Magalhães
Tullio
T
Pozzan
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D002138:Calibration; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018715:Microscopy, Video; D008928:Mitochondria / Q000378:metabolism*; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000378:metabolism*; D017785:Photons; D010957:Plasmids / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D002118:Calcium