Ratiometric intracellular calcium imaging in the isolated beating rat heart using indo-1 fluorescence

Abnormalities in intracellular calcium (Ca-i(2+)) handling have been implicated as the underlying mechanism in a large number of pathologies in the heart. Study into the relation between Ca-i(2+) behavior and performance of the whole heart function could provide detailed information into the cellular basis of heart function. In this study we describe an optical ratio imaging setup and an analysis method for the beat-to-beat Ca-i(2+) videofluorescence images of an indo-1 loaded, isolated Tyrode-perfused beating rat heart. The signal-to-noise ratio and the spatiotemporal resolution (with an optimum of 1 ms and 0.6 mm, respectively) made it possible to register different temporal Ca-i(2+) transients together with left ventricle pressure changes. The Ca-i(2+) transients showed that Ca-i(2+) activation propagates horizontally from left to right during sinus rhythm or from the stimulus site during direct left ventricle stimulation. The indo-1 ratiometric video technique developed allows the imaging of ratio changes of Ca-i(2+) with a high temporal (1 ms) and spatial (0.6 mm) resolution in the isolated Tyrode-perfused beating rat heart