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SPECIES‐INDEPENDENT METABOLIC RESPONSE TO AN INCREASE OF [Ca 2+ ] i IN QUIESCENT CARDIAC MUSCLE
Author(s) -
Ward MarieLouise,
Cooper Patricia J,
Hanley Peter J,
Loiselle Denis S
Publication year - 2003
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1046/j.1440-1681.2003.03877.x
Subject(s) - extracellular , chemistry , intracellular , contraction (grammar) , calcium , biophysics , cardiac muscle , medicine , analytical chemistry (journal) , endocrinology , biochemistry , biology , chromatography , organic chemistry
Summary 1. The aim of the present investigation was to contrast the Ca 2+ dependence of cardiac energy metabolism in two species with differential reliance on extracellular Ca 2+ for excitation–contraction coupling. 2. We measured energy expenditure as the rate of oxygen consumption (V̇ o 2 ) of isolated, Langendorff‐perfused hearts of rats and guinea‐pigs during KCl arrest. In parallel experiments, we indexed intracellular Ca 2+ concentration ([Ca 2+ ] i ) of isolated right‐ventricular trabeculae, using the Ca 2+ fluorophore fura‐2 and ratiometric spectrofluorometry. By varying extracellular Na + concentration ([Na + ] o ), V̇ o 2 –[Na + ] o and [Ca 2+ ] i –[Na + ] o relationships were constructed for each species. 3. Reduction of [Na + ] o during K + arrest caused pronounced species‐dependent elevations of both V̇ o 2 and [Ca 2+ ] i . Despite the species dependence of both V̇ o 2 and [Ca 2+ ] i on [Na + ] o , a single species‐independent V̇ o 2 –[Ca 2+ ] i relationship obtained. 4. We infer that elevation of the metabolic rate of the arrested heart above its basal value is determined primarily by [Ca 2+ ] i and is not species dependent.