Figure 2.
Dependence of endocytic event properties on [Ca2+]e. A, The number of endocytic events within 5 min of cell-attached recordings was reduced by ∼70% at 0.5 mm [Ca2+]e (n = 102 patches) (p < 0.01) and by ∼95% at zero [Ca2+]e (n = 46 patches) (p < 0.01), compared to 2 mm [Ca2+]e (n = 95 patches). Zero [Ca2+]e was achieved through a combination of removal of Ca2+ and addition of 5 mm EGTA. B, The number of amperometric spikes at 0.5 mm [Ca2+]e (n = 18 cells) was reduced compared to 2 mm [Ca2+]e (n = 18 cells) (p < 0.01). The experiments in A and B were performed on different cells from the same preparations. C, The endocytosis/exocytosis ratio did not differ statistically between 2 and 0.5 mm [Ca2+]e (p > 0.05). D, Representative fission-pore events at 2 mm (left) and 0.5 mm [Ca2+]e (right) in the cell-attached patch configuration. E, The mean capacitance step size of endocytic vesicles was indistinguishable between these two groups (2 mm [Ca2+]e: n = 43 events; 0.5 mm [Ca2+]e: n = 42 events) (p > 0.05). F, The fission-pore Gp was independent of [Ca2+]e (p > 0.05). G, The fission-pore duration was significantly increased (p < 0.01) at 0.5 mm [Ca2+]e. **p < 0.01.