title: Mitochondrial Ca2+ uptake, efflux, and sarcolemmal damage in Ca2+-overloaded cultured rat cardiomyocytes.
abstract: The purpose of this study was to determine mitochondrial Ca2+ accumulation and its possible role in initiation of mitochondrial permeability transition (MPT) and sarcolemmal damage in Ca2+-overloaded cardiomyocytes. Cellular Ca2+ overload, generated secondary to ouabain or p-chloromercuribenzoate-stimulated cell Na+ concentration increase, induced Ca2+ accumulation in mitochondria (approximately 3/4 of total net uptake) as identified by kinetic analysis and verified by use of mitochondrial inhibition. Mitochondrial Ca2+ uptake was followed by a rapid Ca2+ efflux ( approximately 1 mmol . kg dry wt-1 . min-1) that can be best explained by efflux via Ca2+-dependent nonspecific pores. Cell ATP concentration was stable during mitochondrial Ca2+ uptake and decreased in parallel with Ca2+ efflux. In addition, sarcolemmal damage was not related to the increase in mitochondrial Ca2+ concentration per se, but rather connected with the extent of Ca2+ efflux from the mitochondria. A decrease in the rate of this Ca2+ efflux, indicating also a decrease in a subpopulation of mitochondria with open pores, was followed by decreased sarcolemmal damage. Both dithiothreitol and cyclosporin A decreased rapid Ca2+ efflux and inhibited sarcolemmal damage, implicating MPT as an important component in the mechanism of sarcolemmal damage.
authors.affiliation: Department of Physiology, University of California Los Angeles School of Medicine, Los Angeles, California 90095-1760, USA.
authors.forename: P
authors.initials: P
authors.lastname: Korge
authors.forename: G A
authors.initials: GA
authors.lastname: Langer
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000008:administration & dosage / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000187:drug effects; D020245:p-Chloromercuribenzoic Acid / Q000494:pharmacology
chemical_list: D002316:Cardiotonic Agents; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D020245:p-Chloromercuribenzoic Acid; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium