Cytosolic free calcium concentration in individual cardiac myocytes in primary culture

J. Y. Cheung, D. L. Tillotson, R. V. Yelamarty, R. C. Scaduto

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Cytosolic free Ca2+ concentration, [Ca2+](i), of single isolatd Ca2+-tolerant rat ventricular myocytes in primary culture was determined by digital video imaging of intracellular fura-2 fluorescence. In deenergized myocytes in which contractile elements were uncoupled by 2,3-butanedione monoxime, the maximum and minimum fluorescence intensity ratio values of fura-2 in the cell were similar when compared with those of fura-2 solutions observed in the microscope. Through the use of in vitro calibration [Ca2+](i) in quiescent, rod-shaped myocytes was 90 ± 6 nM. There was no detectable spatial heterogeneity in [Ca2+](i) in resting myocytes. Localized regions of [Ca2+](i) elevation were observed in cells undergoing spontaneous rhythmic contractions or when subjected to mild depolarization by KCl. Additions of gramicidin or veratridine resulted in massive increases in [Ca2+](i) (>1 μM) and immediate cell hypercontracture. Ruthenium red elicited a modest increase in [Ca2+](i) but extracellular ATP or epinephrine had no effect. We conclude the following: 1) digital video imaging of resting cardiac cells did not reveal any subcellular Ca2+ gradients; 2) the fluorescence properties of intracellular fura-2 were similar to that in free solution; and 3) subcellular heterogeneity of [Ca2+](i) in isolated myocytes was observed in cells undergoing spontaneous rhythmic contraction.

Original languageEnglish (US)
Pages (from-to)25/6
JournalAmerican Journal of Physiology - Cell Physiology
Issue number6
StatePublished - 1989

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cell Biology


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