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Effect of calmodulin antagonists on hypoxia and reoxygenation damage in isolated rabbit hearts
Abstract:
The effect of calmodulin antagonists trifluoperazine (2.5 X 10(-7) M and 2.5 X 10(-6) M) and R 24571 (10(-8) M and 10(-7) M) on Langendorff-perfused rabbit hearts subjected to 180 min hypoxia and 30 min reoxygenation was studied. Coronary flow, force of contraction, oxygen consumption and release of lactate, noradrenaline and LDH were measured. Both drugs were found to reduce some of the deleterious consequences of hypoxia, i.e., they caused: marked reduction in the hypoxic LDH release; reduction in hypoxic contracture; increased recovery of active tension, oxygen consumption and coronary flow upon reoxygenation as compared to those in the untreated controls. The drugs prevented reoxygenation-induced LDH release in the drug-pretreated hearts and had no effect when given only during reoxygenation. This suggests that the drugs do not prevent reoxygenation damage as such, but only some changes developing during hypoxia, which make myocardium vulnerable to the reoxygenation damage. Although other interpretations are possible (e.g., the effects are related to the membrane stabilizing action of the drugs), our data are consistent with the hypothesis that a calmodulin-sensitive process is involved in the hypoxia damage of the myocardium.
Insights
Calmodulin antagonists protected rabbit hearts from hypoxia damage by reducing lactate dehydrogenase release and improving recovery after reoxygenation. These findings suggest a calmodulin-sensitive process contributes to myocardial injury during oxygen deprivation.
Area of Science:
- Cardiology
- Biochemistry
- Pharmacology
Background:
- Hypoxia and reoxygenation can cause significant myocardial damage.
- Calmodulin plays a role in cellular responses to stress.
- Understanding protective mechanisms against cardiac ischemia is crucial.
Purpose of the Study:
- To investigate the protective effects of calmodulin antagonists on isolated rabbit hearts subjected to hypoxia and reoxygenation.
- To determine if calmodulin inhibition can mitigate hypoxia-induced cardiac injury.
- To explore the role of calmodulin in myocardial vulnerability during ischemic events.
Main Methods:
- Langendorff-perfused rabbit hearts were exposed to 180 minutes of hypoxia followed by 30 minutes of reoxygenation.
- Hearts were treated with calmodulin antagonists trifluoperazine or R 24571.
- Measurements included coronary flow, contractility, oxygen consumption, and release of lactate, noradrenaline, and lactate dehydrogenase (LDH).
Main Results:
- Calmodulin antagonists significantly reduced hypoxic release of lactate dehydrogenase (LDH).
- The drugs lessened hypoxic contracture and improved recovery of active tension, oxygen consumption, and coronary flow post-reoxygenation.
- Pretreatment with drugs prevented reoxygenation-induced LDH release, while administration during reoxygenation had no effect.
Conclusions:
- Calmodulin antagonists offer protection against hypoxia-induced myocardial damage, not reoxygenation injury itself.
- The protective effects suggest a calmodulin-sensitive process is involved in hypoxia-related myocardial vulnerability.
- Data support the hypothesis that calmodulin plays a role in cardiac injury during oxygen deprivation, potentially via membrane stabilization.