Figure 1. Effect of Ang II on contraction and pH_i.

A, upper panel, a typical continuous recording of cell length showing the time course of the Ang II-induced positive inotropic effect. Middle panel, individual twitch contractions at the times indicated by the letters a–c on the continuous chart recording. Lower panel, effect of Ang II on pH_i. Ang II produced a slow increase in pH_i. B, the overall results of these experiments (n = 9) indicating the temporal dissociation between the positive inotropic and alkalising effect of Ang II. The Ang II-induced positive inotropic effect peaked before any significant change in pH_i (ΔpH_i) could be detected. The increase in pH_i became significant when the positive inotropic effect of Ang II was already fading. Data points are means of five successive pH_i and contraction amplitude measurements (sampling rate 0.5 Hz) from each experiment at every given time. Basal pH_i value before Ang II administration was 7.31 ± 0.05.