Ca²⁺-handling properties determined in isolated FURA2/AM loading atrial myocytes during increasing stimulation frequency from 2–5 Hz.

<p>A, Exemplary recordings of Ca²⁺-transients in Low Capacity Runner (LCR)- and High Capacity Runner (HCR) rats. B, Exemplary tracings of one single twitch Ca²⁺ transient at 2 hz (left panel) 5 hz (right panel) with comparison of LCR and HCR (normalized diastolic Ca²⁺ levels). C, Ca²⁺-amplitude during systolic contraction of the atrial myocytes. D, Diastolic Ca²⁺-level measured at end diastole. E, Time to 50% Ca²⁺-removal during diastole. All Ca²⁺-recordings are presented as the 340/380 ratio of FURA2/AM. n = 5 animals, n = 4−6 cells from each animal. Data are presented as mean±SD.