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Effect of hypothermic cardioplegia on cardiac protection--I. Effect of hypothermic cardioplegia on the cytosolic Ca2+ concentration in rat ventricular myocytes.

Abstract
Cytosolic Ca2+ concentration of rat ventricular cells was measured under varying experimental conditions by using a fluorescent Ca2+ indicator, Fura-2. Resting [Ca2+]i of rat myocyte was 150 +/- 30 nM (n = 39), and this value was compatible with others. The Perfusion of cardioplegic solution significantly increased [Ca2+]i, and this effect was further augmented by hypothermia (p < 0.05). Application of nifedipine (5 x 10(-7) M) to the perfusate or pretreatment of caffeine (10 mM) had no apparent effect on this cardioplegia-induced [Ca2+]i change. But Ni2+ (5 mM), an antagonist of Na+/Ca2+ exchange mechanism, prevented the [Ca2+]i change during cardioplegia (p < 0.05). Magnitude of cardioplegia-induced [Ca2+]i increase was also dependent on the Ca2+ concentration of cardioplegic solution. These results suggest that Na+/Ca2+ exchange may play an important role in cardioplegia-induced [Ca2+]i change. To rule out the possibility whether the protective effect of hypothermic cardioplegia is due to the preservation of high-energy phosphate store or decreasing the transmembrane ionic fluxes by phase transition, we exhausted a energy store of cardiac cell by application of 2,4 dinitrophenol to the bath and measured its effect on [Ca2+]i change during cardioplegia. Hypothermic cardioplegia delayed the onset of [Ca2+]i increase and decreased its amplitude compared to those of normothermic cardioplegia. From the above results, hypothermic cardioplegia may protect the cardiac cells from ischemic insult by preserving a high-energy phosphate store. Application of Ni2+ to the cardioplegic solution or reduction of external Ca2+ concentration also had some protective effect, since it prevented [Ca2+]i increase during cardioplegia.
AuthorsD S Ahn, Y H Lee, D H Kang, B S Kang
JournalYonsei medical journal (Yonsei Med J) Vol. 35 Issue 2 Pg. 162-76 (Jun 1994) ISSN: 0513-5796 [Print] Korea (South)
PMID8091793 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Calcium
Topics
  • Animals
  • Calcium (metabolism)
  • Cytosol (metabolism)
  • Heart Arrest, Induced
  • Heart Ventricles (metabolism)
  • Hypothermia, Induced
  • Myocardial Ischemia (metabolism, prevention & control)
  • Myocardium (metabolism)
  • Rats

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