Table I. Proportion of all exocytic events attributable to sequential exocytosis under various experimental conditions.
| Proportion of sequential exocytosis
|
|||
|---|---|---|---|
| Condition | Exocytosis | En face eventsa | Total eventsa |
| events cell−1 min−1 | % | % | |
| Acinar cells | |||
| 100 pM cholecystokinin | >50 | >50 | |
| Islet cells | |||
| 20 mM glucose | 11.2 | 2.6 (77) | 1.9 (693) |
| 20 mM glucose + 2 μM forskolin | 26.7 | 2.4 (84) | 1.0 (964) |
| 20 mM glucose + 400 nM PMA | 44.8 | 2.0 (51) | 2.3 (651) |
| 20 mM glucose (35°C) | 21.5 | 1.9 (92) | 3.6 (388) |
| 20 mM glucose + 2 μM forskolin (35°C) | 45 | 4.5 (224) | |
| 20 mM glucose + 400 nM PMA (35°C) | 40 | 3.9 (102) | |
| 60 mM KCl | 18.8 | 1.3 (521) | |
| 100 μM acetylcholine | 6.8 | 1.2 (243) | |
| NP-EGTA | 48.6 | 2.4 (83) | 3.3 (563) |
| 20 mM glucose + 2 μM forskolin (15 mM methyl-β-cyclodextrin) |
4.8 | 8.9 (416) | |
The data for acinar cells are from Nemoto et al. (2001). The contribution of sequential exocytosis to total exocytic events was significantly different from the value (2.6%) for en face events during glucose stimulation only in methyl-β-cyclodextrin–treated preparations (χ2 test, P < 0.01).
a
Numbers in parentheses refer to the number of events analyzed.