ISSN:
1440-1681
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
1. The aim of the present investigation was to contrast the Ca2+ dependence of cardiac energy metabolism in two species with differential reliance on extracellular Ca2+ for excitation–contraction coupling.2. We measured energy expenditure as the rate of oxygen consumption (V̇o2) of isolated, Langendorff-perfused hearts of rats and guinea-pigs during KCl arrest. In parallel experiments, we indexed intracellular Ca2+ concentration ([Ca2+]i) of isolated right-ventricular trabeculae, using the Ca2+ fluorophore fura-2 and ratiometric spectrofluorometry. By varying extracellular Na+ concentration ([Na+]o), V̇o2–[Na+]o and [Ca2+]i–[Na+]o relationships were constructed for each species.3. Reduction of [Na+]o during K+ arrest caused pronounced species-dependent elevations of both V̇o2 and [Ca2+]i. Despite the species dependence of both V̇o2 and [Ca2+]i on [Na+]o, a single species-independent V̇o2–[Ca2+]i relationship obtained.4. We infer that elevation of the metabolic rate of the arrested heart above its basal value is determined primarily by [Ca2+]i and is not species dependent.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1440-1681.2003.03877.x
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