Ca2+ preconditioning elicits a unique protection against the Ca2+ paradox injury in rat heart: Role of adenosine

Muhammad Ashraf, J. Suleiman, M. Ahmad

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


Repeated Ca2+ depletion and repletion of short duration, termed Ca2+ preconditioning (CPC), is hypothesized to protect the heart from lethal injury after exposing it to the Ca2+ paradox (Ca2+ PD). Hearts were preconditioned with five cycles of Ca2+ depletion (1 minute) and Ca2+ repletion (5 minutes). These hearts were then subjected to Ca2+ PD, ie, one cycle of Ca2+ depletion (10 minutes) and Ca2+ repletion (10 minutes). Hearts subject to the Ca2+ PD underwent rapid necrosis, and myocytes were severely injured. CPC hearts showed a remarkable preservation of cell structure; ie, 65% of the cells were normal in CPC hearts compared with 0% in the Ca2+ PD hearts. LDH release was significantly reduced in CPC hearts compared with Ca2+ PD hearts (2.45±0.18 and 8.02±0.7 U · min-1 · g- 1, respectively). ATP contents of CPC hearts were less depleted compared with the Ca2+ PD hearts (5.9±0.8 and 3.0±0.16 μmol/g dry weight, respectively). Addition of the adenosine A1 receptor agonist R- phenylisopropyl adenosine before and during Ca2+ PD provided protection similar to that in CPC hearts, whereas the nonselective adenosine A1 receptor antagonist, 8-(p-sulfophenyl)-theophylline, blocked the beneficial effects of CPC. CPC-mediated protection was aborted when hearts subjected to CPC were treated with pertussis toxin (the guanine nucleotide or G-protein inhibitor). The present study suggests that Ca2+ preconditioning confers significant protection against the lethal injury of Ca2+ PD in rat hearts. Cardioprotection appears to result from adenosine release during preconditioning and by G(i)-protein-modulated mechanisms.

Original languageEnglish (US)
Pages (from-to)360-367
Number of pages8
JournalCirculation research
Issue number2
StatePublished - 1994
Externally publishedYes


  • Ca paradox
  • G proteins
  • adenosine
  • adenosine A receptor
  • preconditioning

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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