Ischemic preconditioning prevents calpain-mediated impairment of Na+/K+-ATPase activity during early reperfusion.
OBJECTIVE
We previously demonstrated that ischemic preconditioning (IPC) attenuates calpain activation during reperfusion. Herein, we tested the hypothesis that enhancement of Na+/K+-ATPase activity during early reperfusion as a result of calpain inhibition is involved in the protection afforded by myocardial IPC.


METHODS
Intracellular Na+ concentration ([Na+]i) measured using 23Na-magnetic resonance spectroscopy, Na+/K+-ATPase activity, detachment of Na+/K+-ATPase alpha subunits from the membrane cytoskeleton, degradation of fodrin and ankyrin, and calpain activation were analysed in isolated rat hearts reperfused after 60 min of ischemia with or without previous IPC and different treatments aimed to mimic or blunt the effects of IPC.


RESULTS
In non-treated hearts subjected to ischemia (control hearts), reperfusion for 5 min severely reduced Na+/K+-ATPase activity and dissociated alpha1 and alpha2 subunits of Na+/K+-ATPase from the membrane-cytoskeleton complex in parallel with proteolysis of alpha-fodrin and ankyrin-B and calpain activation. IPC accelerated the recovery of [Na+]i, increased Na+/K+-ATPase activity, and prevented dissociation of Na+/K+-ATPase from the membrane-cytoskeleton complex. IPC also prevented alpha-fodrin and ankyrin-B loss and calpain activation, effects that were associated with attenuated lactate dehydrogenase (LDH) release and infarct size and improved contractile recovery. These effects of IPC were reproduced by perfusing the hearts with the calpain inhibitor MDL-28170 and by transient stimulation of cAMP-dependent protein kinase (PKA) with CPT-cAMP, and they were reverted by perfusing with the PKA inhibitor H89.


CONCLUSIONS
The results of the present study are consistent with the hypothesis that enhanced recovery of Na+/K+-ATPase activity during reperfusion as a result of attenuated calpain-mediated detachment of the protein from the membrane-cytoskeleton complex contributes to the protection afforded by IPC.
Servicio de Cardiologia, Hospital Universitari Vall d'Hebron, Passeig Vall d'Hebron, 119-129, 08035 Barcelona, Spain.
Javier
J
Inserte
David
D
Garcia-Dorado
Victor
V
Hernando
Ignasi
I
Barba
Jordi
J
Soler-Soler
D000818:Animals; D017487:Ankyrins / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D007546:Isoquinolines / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008840:Microfilament Proteins / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013053:Spectrophotometry; D013449:Sulfonamides / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013049:Spectrin
D017487:Ankyrins; D000252:Calcium-Transporting ATPases; D002154:Calpain; D002352:Carrier Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D004151:Dipeptides; D007546:Isoquinolines; D007770:L-Lactate Dehydrogenase; D008840:Microfilament Proteins; D010042:Ouabain; D011493:Protein Kinase C; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D013449:Sulfonamides; D013873:Thionucleotides; D013049:Spectrin; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C058076:calpain inhibitor III