Increase vs. decrease of calcium uptake by isolated heart cells induced by H/sub 2/O/sub 2/ vs. HOCl

Journal Article · Wed Mar 01 04:00:00 EST 1989 · Am. J. Physiol.; (United States)

OSTI ID:6071907

Kaminishi, T; Matsuoka, T; Yanagishita, T; Kako, K J

Adult rat heart myocytes were labeled rapidly with exogenous (45Ca2+). Addition of 2.5 mM H2O2 to the heart cell suspension raised the content of rapidly exchangeable intracellular Ca2+ twofold, whereas addition of 1-30 mM HOCl decreased the Ca2+ content. The H2O2-induced increase in Ca2+ content was dependent on the medium Na+, pH, and temperature but was not significantly affected by addition of verapamil, diltiazem, amiloride, or 3-aminobenzamide. The (3H)ouabain binding to myocytes was suppressed by H2O2, whereas the Ca2+ efflux from myocytes was not influenced. An uncoupler, carbonyl cyanide m-chlorophenylhydrazone, reduced Ca2+ content, implying that the H2O2-induced change in Ca2+ content was not directly related to ATP depletion. On the other hand, the H2O2-induced Ca2+ accumulation in myocytes was prevented by deferoxamine or o-phenanthroline. These results suggest that H2O2 inhibited Na+-K+-ATPase, resulting in an increase in intracellular Na+ concentration and stimulation of sarcolemmal Na+-Ca2+ exchange activity, which caused a transient net Ca2+ influx into myocytes. By contrast, HOCl decreased the Ca2+ content of the rapidly exchangeable pool below control levels and this action of HOCl was antagonized by 1,4-dithiothreitol. HOCl accelerated Ca2+ efflux from myocytes. Ca2+ uptake and Ca2+-ATPase of the isolated sarcoplasmic reticular (SR) fraction were highly sensitive to the action of HOCl. Ca2+ uptake by intracellular sites, studied with myocytes permeabilized with digitonin, was inhibited by both H2O2 and HOCl. Thus these results suggest that HOCl inhibits the SR Ca2+ pump, resulting in the observed acceleration of Ca2+ efflux from and decline in Ca2+ content of myocytes.

• Research Organization: Univ. of Ottawa, School of Medicine, Ontario (Canada)
• OSTI ID: 6071907
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 256; ISSN AJPHA
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACID ANHYDRASES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMAL CELLS
ANIMALS
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BODY
CALCIUM
CALCIUM 45
CALCIUM ISOTOPES
CARDIOVASCULAR AGENTS
CARDIOVASCULAR SYSTEM
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DRUGS
ELEMENTS
ENZYMES
EVEN-ODD NUCLEI
HEART
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
MAMMALS
MEMBRANE TRANSPORT
METALS
MUSCLES
MYOCARDIUM
NUCLEI
ORGANOIDS
ORGANS
OXYGEN COMPOUNDS
PEROXIDES
PHOSPHOHYDROLASES
RADIOISOTOPES
RATS
RODENTS
SARCOPLASMIC RETICULUM
TRACER TECHNIQUES
TRITIUM COMPOUNDS
UPTAKE
VASODILATORS
VERTEBRATES