title: Species dependence of mitochondrial calcium transients during excitation-contraction coupling in isolated cardiomyocytes.
abstract: Whether mitochondrial Ca(2+) transport is rapid enough to respond to changes in cytosolic [Ca(2+)] ([Ca(2+)](c)) which occur during excitation-contraction coupling in the heart is controversial; different results wereobtained with different techniques and different species. In this study mitochondrial [Ca(2+)] ([Ca(2+)](m)) was measured in indo-1/AM-loaded myocytes from rat and guinea-pig hearts where the cytosolic indo-1 had been removed by extended incubation of cells at 37 degrees C ("heat treatment"). The mitochondrial origin of the remaining fluorescence was confirmed by sensitivity of the indo-1 signal to ruthenium red. In resting rat myocytes, [Ca(2+)](m) was lower than [Ca(2+)](c), whereas in guinea-pig cells [Ca(2+)](m) was higher than [Ca(2+)](c). Upon electrical stimulation of cells, no change occurred in [Ca(2+)](m) in rat myocytes. However, in guinea-pig cells mitochondrial Ca(2+) transients were clearly visible with a mean indo-1 ratio amplitude of 0.153 +/- 0.2 (n = 20), compared with 0.306 +/- 0.02 (n = 25), p < 0.001, prior to heat treatment. These observations suggest significant differences in mitochondrial Ca(2+) transport in cardiomyocytes from different species.
authors.affiliation: Bristol Heart Institute, University of Bristol, United Kingdom.
authors.forename: E J
authors.initials: EJ
authors.lastname: Griffiths
mesh_terms: D000818:Animals; D001692:Biological Transport; D020013:Calcium Signaling / Q000502:physiology*; D002469:Cell Separation; D004734:Energy Metabolism; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D007211:Indoles; D008297:Male; D008929:Mitochondria, Heart / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D012430:Ruthenium Red; D013045:Species Specificity
chemical_list: D007211:Indoles; D012430:Ruthenium Red; C059587:Indo-1 pentaacetoxymethyl ester