Antagonists of calmodulin delay injury development in the severely ischemic perfused working rat heart

The effects of calmodulin antagonists trifluoperazine (TFP) and calmidazolium (CMZ) and of ethmozine (a phenothiazine without anticalmodulin activity) on the postischemic recovery in the perfused working rat hearts were studied. In the hearts subjected to 25 min zero-flow ischemia coronary flow, cardiac output, MVO2 and external work recovered to about 50% of the preischemic values during 40 min of reperfusion. TFP (5 x 10(-7) M and 10(-6) M) or CMZ (10(-7) M) improved the functional recovery to 75-94% whereas 5 x 10(-7) M ethmozine was not effective. In all experimental groups a prolongation of the ischemic period caused a progressive deterioration of the functional recovery while the total postischemic LDH release showed an initial gradual rise followed by a later decay. TFP and CMZ prolonged the time-to-half decay of the hemodynamic functions (tHF50) by 4-7 min and the time-to-peak of total LDH release (tLDHmax) by 5-10 min. In the hearts subjected to 0.2 ml/min low-flow ischemia tHF50 and tLDHmax were increased to 40 min, CMZ prolonged these times by further 5-10 min. Thus, TFP and CMZ delayed the development of the myocardial ischemic injury. Although other interpretations are possible, our data are consistent with the hypothesis that calmodulin-sensitive process is involved in the ischemic damage of the myocardium.