Figure 3. Exocytosis is augmented by Ca²⁺ and ATP.

A, representative traces of ΔC_m for cells infused with intracellular solutions containing 0.1 mm cAMP and 1.5 μm free Ca²⁺ with or without 3 mm ATP. B, average ΔC/Δt at indicated time points. The observation that rates of exocytosis are equal at times ≥10 min indicates continuous vesicle replenishment regardless of absence or presence of ATP. Note that analysis at early time points (30 s) show little evidence of net exocytosis after establishment of the whole-cell configuration, before control of the intracellular milieu by infusion of the pipette solution. C and D, as in A and B but cells dialysed with a pipette solution lacking Ca²⁺. The rates of exocytosis in B and D are close to 0 at 30 s, indicating negligible net exocytosis prior to infusion of the pipette solution. Data are mean values ± SEM of: 8 (+ATP) and 7 (–ATP) recordings in B, and 9 (+ATP) and 13 (–ATP) recordings in D. *P < 0.05; **P < 0.01.