Fig. 4.

Effect of the regional increase in [K⁺]_o on spatial changes in [Ca²⁺]_i in the absence of isoproterenol. A: representative recordings of force (top) and spatial changes in [Ca²⁺]_i (bottom) during the last 2 electrical stimuli (400-ms stimulus interval) with (right) and without the regional increase in [K⁺]_o (left). At right, Ca²⁺ surged repeatedly (arrowheads) around the jet-exposed region (IN_jet) and propagated as waves through the trabeculae after the trains of electrical stimuli. Arrows with ST indicate the moments of electrical stimulation. Without the regional increase in [K⁺]_o, the Ca²⁺ waves disappeared (left) ([Ca²⁺]_o = 3.0 mmol/l, temperature = 24.1°C, Experiment Number 090507). B: summary data of the effect of the regional increase in [K⁺]_o on the velocity of Ca²⁺ waves. The propagation velocity of Ca²⁺ waves increased significantly during the regional increase in [K⁺]_o (R), compared with that without the increase (C, n = 9). §P < 0.01 vs. C (Wilcoxon signed-ranks test).