Delayed recovery of intracellular acidosis during reperfusion prevents calpain activation and determines protection in postconditioned myocardium.

Abstract

AIMS:

Indirect data suggest that delayed recovery of intracellular pH (pHi) during reperfusion is involved in postconditioning protection, and calpain activity has been shown to be pH-dependent. We sought to characterize the effect of ischaemic postconditioning on pHi recovery during reperfusion and on calpain-dependent proteolysis, an important mechanism of myocardial reperfusion injury.

METHODS AND RESULTS:

Isolated Sprague-Dawley rat hearts were submitted to 40 min of ischaemia and different reperfusion protocols of postconditioning and acidosis. pHi was monitored by (31)P-NMR spectroscopy. Myocardial cell death was determined by lactate dehydrogenase (LDH) and triphenyltetrazolium staining, and calpain activity by western blot measurement of alpha-fodrin degradation. In control hearts, pHi recovered within 1.5 +/- 0.24 min of reperfusion. Postconditioning with 6 cycles of 10 s ischaemia-reperfusion delayed pHi recovery slightly to 2.5 +/- 0.2 min and failed to prevent calpain-mediated alpha-fodrin degradation or to elicit protection. Lowering perfusion flow to 50% during reperfusion cycles or shortening the cycles (12 cycles of 5 s ischemia-reperfusion) resulted in a further delay in pHi recovery (4.1 +/- 0.2 and 3.5 +/- 0.3 min, respectively), attenuated alpha-fodrin proteolysis, improved functional recovery, and reduced LDH release (47 and 38%, respectively, P < 0.001) and infarct size (36 and 32%, respectively, P < 0.001). This cardioprotection was identical to that produced by lowering the pH of the perfusion buffer to 6.4 during the first 2 min of reperfusion or by calpain inhibition with MDL-28170.

CONCLUSION:

These results provide direct evidence that postconditioning protection depends on prolongation of intracellular acidosis during reperfusion and indicate that inhibited calpain activity could contribute to this protection.

• Authors: Javier Inserte, Ignasi Barba, Víctor Hernando, David Garcia-Dorado
• Journal: Cardiovascular research (Cardiovasc Res) Vol. 81 Issue 1 Pg. 116-22 (Jan 01 2009) ISSN: 1755-3245 [Electronic] England
• PMID: 18829701 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Carrier Proteins
• Microfilament Proteins
• fodrin
• Phosphocreatine
• L-Lactate Dehydrogenase
• Calpain

Topics

• Acidosis (metabolism)
• Animals
• Apoptosis
• Calpain (metabolism)
• Carrier Proteins (metabolism)
• Disease Models, Animal
• Hydrogen-Ion Concentration
• L-Lactate Dehydrogenase (metabolism)
• Male
• Microfilament Proteins (metabolism)
• Myocardial Reperfusion Injury (metabolism, pathology)
• Phosphocreatine (metabolism)
• Rats
• Rats, Sprague-Dawley