Figure 2. The effect of RR on the cytosolic Ca²⁺ transients measured with fura-2 at different frequencies of stimulation.

Ca²⁺ transients from an intact cardiomyocyte electrically stimulated at 0.1 Hz: A, control; B, after incubation in RR (10 μm). Ca²⁺ transients from an intact cardiomyocyte electrically stimulated at 3.0 Hz: C, control; D, after incubation in RR (10 μm). E, the relationship between action of RR (ordinate) and frequency of stimulation (abscissa). The amplitude ratio is the mean amplitude of evoked [Ca²⁺]_c response observed in the presence of RR divided by that recorded in its absence. Points with error bars are the average (±s.e.m.) of 3–8 experiments. *P < 0.05.