Figure 4. Effect of substituting 5 mm ATP with selected nucleotides.

Each point is the mean ± s.e.m. expressed as a percentage of the control response obtained in the presence of 5 mm ATP using the protocol shown in Fig. 2A. Mean Ca²⁺ transient amplitude in the presence of 5 mm ATP or 0.1 mm ATP is shown. Responses obtained in the presence of 0.1 mm ATP and 4.9 mm AMP-PNP, ADP, AMP, adenosine (Adn) or CTP are also given. Responses in the presence of adenosine and CTP are significantly smaller than those obtained in the presence of 0.1 mm ATP alone (P < 0.05). The number of preparations is indicated in parentheses.