FLUOROCARBON SIMULATION OF MYOCARDIAL-ISCHEMIA AND REPERFUSION - STUDIES OF RELATIONSHIPS BETWEEN FORCE AND INTRACELLULAR CALCIUM

Objective: The aim was to compare the effects of simulated ischaemia-r eperfusion with those of hypoxia-reoxygenation in isolated muscle prep arations from the ferret right ventricle. Methods: Ischaemia was simul ated using fluorocarbon immersion plus hypoxia. Intracellular calcium transients were determined from aequorin luminescence during isometric contractions. Results: Hypoxia in fluorocarbon and physiological sali ne solution resulted in a similar reversible depression of the peak of the calcium transient. Peak active tension, however, was more depress ed in fluorocarbon than in physiological salt solution. The dissociati on between peak light and peak active tension was most pronounced on r eoxygenation, with near complete recovery of peak light, while there w as little recovery of tension in fluorocarbon. When fluorocarbon was t hen replaced by physiological salt solution, peak active tension recov ered promptly. A prolongation of the decay of the calcium transient wa s seen in both fluorocarbon and physiological salt solution during hyp oxia, which shortened promptly on reoxygenation. The time to the peak of the calcium transient was most prolonged during hypoxia in fluoroca rbon and there was gradual recovery on reoxygenation. Conclusions: Whi le some changes in the calcium transient during simulated ischaemia ar e rapidly reversible with reoxygenation (in fluorocarbon), suggesting an effect of hypoxia, others are incompletely reversed or only reverse d with physiological salt solution, suggesting an effect of metabolite accumulation. The pronounced dissociation between peak light and peak active tension during reoxygenation in fluorocarbon is promptly rever sed by changing to physiological salt solution, suggesting that metabo lite retention in the postischaemic period may contribute to depressed myocardial function after reperfusion.