Comparison of changes in Ca²⁺ concentration in quail and rat cardiomyocytes using Fura-4F

Abstract

High cardiac pump function in mammals and birds requires the elaborate control of calcium (Ca²⁺) concentrations in cardiomyocytes (CMs). Previously, we reported that avian quail CMs have a higher capacity for Ca²⁺ efflux than mammalian rats, but the decrease in Ca²⁺ concentration estimated using the fluorescent Ca²⁺ indicator Fura-2 was slower than that expected from the observation of cell relaxation behavior. In this study, we examined changes in Ca²⁺ concentration in quail and rat CMs using Fura-4F, which allows for more rapid tracking of changes in Ca²⁺ concentrations than Fura-2. The results demonstrated that, compared to Fura-2, Fura-4F showed a narrower dynamic range but a more rapid response to changes in Ca²⁺ concentration. Furthermore, Fura-4F showed that the Ca²⁺ concentration in quail CMs decreased significantly faster than that in rat CMs after electrical stimulation. These results are qualitatively consistent with our previous study using Fura-2 and therefore reinforce the conclusion that the Ca²⁺ removal capacity of quail CMs is higher than that of rat CMs.