Inhibition of mitochondrial calcium uptake slows down relaxation in mitochondria-rich skeletal muscles.
Isolated fibres from various muscles were skinned mechanically in oil. From a Ca2+-loaded micropipette, local applications of Ca2+ were made. These produced a limited contraction which relaxed spontaneously. The time-course of sarcomere shortening and re-lengthening was recorded by microcinephotography. Application of Ruthenium Red, a potent and specific inhibitor of Ca2+ uptake by mitochondria, did not affect the contraction-relaxation cycles of typical glycolytic white fibres (frog sartorius, pigeon breast). By contrast, Ruthenium Red greatly slowed down the relaxation rate in mitochondria-rich fibres (rat soleus and rabbit masseter). In these fibres, Ca2+ uptake by mitochondria seems to play an active role in promoting relaxation.
Gillis
J M
JM
Department of Physiology, Catholic University of Louvain, Faculty of Medicine, Bruxelles, Belgium.
D000818:Animals; D001001:Anura; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics*; D004396:Coloring Agents / Q000494:pharmacology; D010856:Columbidae; D005990:Glycerol / Q000494:pharmacology; D006019:Glycolysis / Q000502:physiology; D007551:Isotonic Contraction / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000502:physiology*; D010369:Pectoralis Muscles / Q000502:physiology; D016658:Psoas Muscles / Q000502:physiology; D011817:Rabbits; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology
D004396:Coloring Agents; D012430:Ruthenium Red; D005990:Glycerol; D002118:Calcium