Publications (1)3.19 Total impact
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ABSTRACT: Halothane has been shown to be a powerful myocardial protectant during normothermic cardioplegic arrest and subsequent reperfusion. In view of its multiple effects on cellular Ca2+ movements and the role of this ion in ischemia-reperfusion injury, the questions of whether halothane is capable of maximally protecting the heart or whether combination therapy of halothane with other Ca2+ blocking agents may be more effective arose. Therefore, the effects of combination therapy with halothane and a calcium antagonist (nifedipine), or a Na+/H+ inhibitor (HOE 694), or a Na+/Ca2+ inhibitor (quinacrine) on postcardioplegic functional recovery were evaluated. The isolated perfused rat heart subjected to 45 minutes normothermic cardiac arrest was used as an experimental model. Dose-response curves were performed for each drug. Using the optimal dosage for each drug, the following results were obtained: (1) Nifedipine (10(-7) M; administered retrogradely 10 minutes before and after cardioplegia) and halothane (1.5% administered during cardioplegia), when administered separately, improved functional recovery. Combination therapy did not further improve protection. (2) HOE 694 (10(-7) M) or quinacrine (10(-9) M) improved post-cardioplegic functional recovery when added for 2 minutes at the onset of reperfusion. Simultaneous administration of HOE 694 and 1.5% halothane was the only combination that yielded additive protection. (3) Quinacrine, a phospholipase and Na+/Ca2+ exchanger inhibitor, appeared to be the most powerful drug used. In summary, the results obtained indicate that interventions aimed at preventing intracellular Ca2+ overload improve recovery after cardioplegic arrest. The beneficial effects of halothane could be further improved by HOE 694.
Johannesburg, Gauteng, South Africa
- Division of Medical Physiology