Protection against cellular damage in the perfused rat heart by lowered pH.
In this comparative study, rat hearts were perfused at 37 degrees C with three clearly defined protocols: the Ca2+ paradox, the O2 paradox and with 20 mM caffeine. Each protocol involved an initial priming (Ca2+(o) depletion or anoxia; stage 1) and subsequent full activation (Ca2+(o) repletion or reoxygenation; stage 2) of the damage system of the sarcolemma. Creatine kinase release in stage 2 was completely inhibited (P < 0.001) in all three protocols when pH was reduced to 6.5 throughout the experiments, or only during stage 1, or only during stage 2. The inhibitor of the Na+/H+ antiporter, amiloride (1 mM), completely prevented creatine kinase release in the Ca2+ paradox (P < 0.001) and markedly reduced damage in the caffeine protocol. Amiloride had no significant effect on creatine kinase release in the O2 paradox. The possible role of Na+(i) was studied in the caffeine protocol: ouabain (5 x 10(-6) M) had little effect whereas substitution of choline for Na+ in the perfusion medium reduced creatine kinase release by about 50%. It is suggested that the same damage system is activated in stage 1 in all three protocols and that a key event is the intracellular production of H+ which are exported via Na+(o)/H(i) exchange. Prevention of H+ efflux by lowered pH(o), even during stage 2, protected against creatine kinase release. The possible role of Na+ movements in the genesis of sarcolemma damage is discussed.
Harding
R J
RJ
School of Biological Sciences, University of Liverpool, UK.
Duncan
C J
CJ
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000009:adverse effects; D002118:Calcium / Q000009:adverse effects; D003402:Creatine Kinase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology; D066298:In Vitro Techniques; D009206:Myocardium / Q000201:enzymology / Q000473:pathology*; D010042:Ouabain / Q000494:pharmacology; D010100:Oxygen / Q000009:adverse effects; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D012964:Sodium / Q000502:physiology
D002110:Caffeine; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D003402:Creatine Kinase; D010100:Oxygen; D002118:Calcium