Calcium activation of heart mitochondrial oxidative phosphorylation. Rapid kinetics of mV̇O2, NADH, and light scattering

Paul R. Territo, Stephanie A. French, Mary C. Dunleavy, Frank J. Evans, Robert S. Balaban

Research output: Contribution to journalArticle

126 Scopus citations

Abstract

Parallel activation of heart mitochondria NADH and ATP production by Ca2+ has been shown to involve the Ca2+-sensitive dehydrogenases and the F0F1-ATPase. In the current study we hypothesize that the response time of Ca2+-activated ATP production is rapid enough to support step changes in myocardial workload (∼100 ms). To test this hypothesis, the rapid kinetics of Ca2+ activation of mV̇O2, [NADH], and light scattering were evaluated in isolated porcine heart mitochondria at 37 °C using a variety of optical techniques. The addition of Ca2+ was associated with an initial response time (IRT) of mV̇O2 that was dose-dependent with a minimum IRT of 0.27 ± 0.02 s (n = 41) at 535 nM Ca2+. The IRTs for NADH fluorescence and light scattering in response to Ca2+ additions were similar to mV̇O2. The Ca2+ IRT for mV̇O2 was significantly shorter than 1.6 mM ADP (2.36 ± 0.47 s; p ≤ 0.001, n = 13), 2.2 mM Pi (2.32 ± 0.29, p ≤ 0.001, n = 13), or 10 mM creatine (15.6.±1.18 s, p ≤ 0.001, n = 18) under similar experimental conditions. Calcium effects were inhibited with 8 μM ruthenium red (2.4 ± 0.31 s;p ≤ 0.001, n = 16) and reversed with EGTA (1.6 ± 0.44; p ≤ 0.01, n = 6). Estimates of Ca2+ uptake into mitochondria using optical Ca2+ indicators trapped in the matrix revealed a sufficiently rapid uptake to cause the metabolic effects observed. These data are consistent with the notion that extramitochondrial Ca2+ can modify ATP production, via an increase in matrix Ca 2+ content, rapidly enough to support cardiac work transitions in vivo.

Original languageEnglish (US)
Pages (from-to)2586-2599
Number of pages14
JournalJournal of Biological Chemistry
Volume276
Issue number4
DOIs
StatePublished - Jan 26 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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