Metabolic recovery of isolated adult rat cardiomyocytes after energy depletion: existence of an ATP threshold?
The question was investigated whether cardiomyocytes can be resuscitated after extreme energy depletion, i.e. after loss of ATP >70%. Isolated ventricular cardiomyocytes of the adult rat were exposed to metabolic inhibition with dinitrophenol and cyanide (DNP 0.2 mm; KCN 2 mm). After rapid energy depletion, cells were "reoxygenated" by wash-out of DNP and KCN. Intracellular calcium, cell length, ATP and creatine phosphate (CrP) of the cardiomyocytes were monitored. Metabolic inhibition resulted in a depletion of the stores of ATP and CrP by more than 95% of the normoxic values and caused a cytosolic Ca2+ overload. Parameters of metabolic recovery were: (i) resynthesis of CrP; (ii) recovery of a normal cytosolic Ca2+ control; and (iii) the elicitation of energy-dependent hypercontracture. "Reoxygenation", i.e. wash-out of metabolic inhibitors, reactivated oxidative phosphorylation. Consecutively, CrP levels recovered to 76.0+/-7.3%, ATP levels recovered to 10. 4+/-2.3% (means+/-s.dn=10) of the initial normoxic values, a normoxic intracellular calcium level was re-established and hypercontracture was elicited. Prolongation of metabolic inhibition with KCN (2 mm) or inhibition of the Na+/K+ pump with ouabain (0.5 mm) disabled the cardiomyocytes to recover from cytosolic Ca2+ overload and prevented hypercontracture. It is concluded that even after extensive energy depletion metabolic resuscitation of the myocardial cell remains possible and a critical range of ATP for recovery, i.e. a "threshold" of a 70% loss of ATP, does not exist.
Bonz
A
A
Chirurgische Universitätsklinik, Abt. Herzchirurgie, Universität Heidelberg, Im Neuenheimer Feld 110, D-69120 Heidelberg, Germany.
Siegmund
B
B
Ladilov
Y
Y
Vahl
C F
CF
Piper
H M
HM
D000138:Acidosis; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004140:Dinitrophenols / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects; D006352:Heart Ventricles; D007700:Kinetics; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010085:Oxidative Phosphorylation; D010725:Phosphocreatine / Q000378:metabolism; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D004140:Dinitrophenols; D010725:Phosphocreatine; D010042:Ouabain; D000255:Adenosine Triphosphate; D011190:Potassium Cyanide; D002118:Calcium