Pretreatment with PKC activator protects cardiomyocytes against reoxygenation-induced hypercontracture independently of Ca2+ overload.
OBJECTIVE
Although several studies have shown that activation of protein kinase C (PKC) plays an important role in protection through ischemic preconditioning, little is known about the effects of direct PKC activation on the course of ischemia-reperfusion injury. The aim of this study was to analyse the effects of a pretreatment with the PKC activator 1,2-dioctanoyl-sn-glycerol (1,2DOG).


METHODS
Isolated adult Wistar rat cardiomyocytes were exposed to 80 min of simulated ischemia (anoxia, pHo 6.4) and 20 min of reoxygenation (pHo 7.4). Cytosolic Ca2+ (fura-2), cytosolic pH (BCECF), Mg2+ (Mg-fura-2), lactate and cell length were measured and compared between control cells and cells treated with 20 mumol/l 1,2DOG before anoxia (10 min treatment and 10 min wash out).


RESULTS
1,2DOG-pretreatment delayed the time to extreme ATP depletion, but had no effect on lactate production and cytosolic pH. The accumulation of cytosolic Ca2+ was markedly accelerated in pretreated cells that developed rigor shortening, but reoxygenation-induced hypercontracture was significantly reduced. 1,2DOG, therefore, completely abolished Ca(2+)-dependence of hypercontracture. The effects of pretreatment were fully abolished with 1 mumol/l bisindolylmalcimide (PKC inhibitor). We conclude that PKC preactivation leads to (1) reduction of energy demand, (2) acceleration of Ca2+ overload during anoxia and (3) prevention of reoxygenation-induced hypercontracture independent of anoxic changes in cytosolic Ca2+ and pH.
Ladilov
Y V
YV
Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany.
Balser-Schäfer
C
C
Haffner
S
S
Maxeiner
H
H
Piper
H M
HM
D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology*; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D004075:Diglycerides; C044295:1,2-dioctanoylglycerol; D019344:Lactic Acid; D011493:Protein Kinase C; D008274:Magnesium; D002118:Calcium