Fig. 4.

Cell shortening and Ca2+ kinetics. A. Representative recordings of sarcomere shortening and Calcium transient during electrical stimulation in WT and KI cells isolated from 6-month-old mice. Data represent means ± SD of 24–33 cells from 3 preparations. B. SR calcium content measured by caffeine application, with or without 10 nM isoproterenol. Data represent means ± SEM of 12–20 cells from 3 preparations. C. Representative recordings of spontaneous Ca2+ transients during sequential pacing of isolated cardiomyocytes. Spontaneous Ca2+ transients were observed in homozygous KI mice. The occurrence of evoked Ca2+ transients was shown in the bar graph. Data represent means ± SD of 188–246 cells from 3 to 4 preparations.