Figure 1.

Supramaximal CCK-8 stimulation inhibits the later phases of acinar secretion mediated by VAMP8. Isolated WT mouse pancreatic acini were left untreated (Basal), stimulated with 100 pm CCK-8 (Max), or 10 nm CCK-8 (Supramax) for 30 min. A, acini and media were sequentially removed from the same batch of cells and analyzed for amylase release at indicated time points. Dashed lines indicate the slopes of first- and second-phase secretion. B, the rate of amylase release over each 2-min interval. Dashed lines denote the first (0–2 min) and second (2–10 min) phases of secretion. The third phase of secretion (10–30 min) is not denoted by a dashed line. Note that Supramax CCK-8 greatly diminishes the second and third phases of secretion. C, WT or VAMP8^−/− acini were cultured for 4 h with adenovirus (4 × 10⁶ pfu/ml) expressing GFP control or TeTx light chain to cleave VAMP2. D52 and VAMP2 levels were analyzed by immunoblot. D, Max (30 pm) or Supramax (30 nm) CCK-8-stimulated total amylase secretion from GFP- or TeTx-expressing acini (30 min) (data are the mean and S.E. *, p < 0.05 Max to Supramax CCK-8). E, Supramax CCK-8-induced secretory inhibition was calculated as the percent of Max CCK-8 stimulation (data are the mean and S.E. * p < 0.05 to respective GFP control). All experiments were generated from at least three separate acinar preparations, performed in duplicate.