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Myocardial Na+ during ischemia and accumulation of Ca2+ after reperfusion: a study with monensin and dichlorobenzamil.

Abstract
The intracellular cation contents were determined in isolated perfused rat heart using cobaltic EDTA as a marker of the extracellular space. In hearts in which Na+ accumulation was induced with monensin, a Na+ ionophore, during 20 min-ischemia which otherwise did not result in accumulation of Na+, the levels of Na+ and Ca2+ were significantly higher after reperfusion with a significant decrease in K+. While the recovery of the cardiac mechanical function (CMF) was complete after reperfusion in control hearts, the recovery was incomplete in monensin-hearts. Dichlorobenzamil (DCB), the most specific inhibitor of Na(+)-Ca2+ exchanger, infused for 10 min before induction of ischemia in a dose of 10(-5) M, which produced a definite suppression of CMF (over 80%), inhibited the accumulation of Ca2+ and Na+ and the loss of K+ and ATP after 40 min-ischemia and reperfusion. The same dose of DCB given for 3 min before induction of ischemia and after reperfusion, which produced a less than 20% inhibition of CMF, failed to prevent the Ca2+ accumulation after 40 min-ischemia and reperfusion. These findings are at variance with the idea that the accumulation of Na+ during ischemia and the consequent augmented operation of Na(+)-Ca2+ exchange is responsible for accumulation of Ca2+ after reperfusion.
AuthorsT Kawada, Y Yoshida, H Sakurai, S Imai
JournalJapanese journal of pharmacology (Jpn J Pharmacol) Vol. 59 Issue 2 Pg. 191-200 (Jun 1992) ISSN: 0021-5198 [Print] JAPAN
PMID1434115 (Publication Type: Journal Article)
Chemical References
  • Adenine Nucleotides
  • 3',4'-dichlorobenzamil
  • Amiloride
  • Monensin
  • Sodium
  • Potassium
  • Calcium
Topics
  • Adenine Nucleotides (metabolism)
  • Amiloride (analogs & derivatives, pharmacology)
  • Animals
  • Calcium (metabolism)
  • In Vitro Techniques
  • Ion Transport (drug effects)
  • Male
  • Monensin (pharmacology)
  • Myocardial Ischemia (metabolism, physiopathology)
  • Myocardial Reperfusion Injury (metabolism, physiopathology)
  • Myocardium (metabolism)
  • Perfusion
  • Potassium (metabolism)
  • Rats
  • Sodium (metabolism)

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