Figure 2.

DOC2B^wt enhances secretion during repeated stimulations compared with control and DOC2B^D218,220N. Adult mouse adrenal chromaffin cells were depolarized repeatedly, and CA release was measured by carbon fiber amperometry. A, Mean CA secretion during stimulation of EGFP control (black; n = 18), DOC2B^wt (blue; n = 17), and DOC2B^D218,220N (red; n = 24). Secretion in DOC2B^D218,220N was significantly larger than EGFP controls in the first (**p < 0.01) and second (*p < 0.05) stimulus, but not during subsequent stimuli. DOC2B^wt significantly enlarged the secretory response from the second stimulus on (*p < 0.05). B–E, Integration of the amperometric currents of the first four stimulations, respectively. B, During the first stimulation, the secretion slope is much steeper in DOC2B^D218,220N than in DOC2B^wt and the EGFP control. C, At the second stimulation, both DOC2B^D218,220N and DOC2B^wt support significant increased secretion, and their slopes are similar. D, E, During the third and fourth stimulations, the secretion slopes of DOC2B^wt and DOC2B^D218,220N are steeper than EGFP control cells, whereas secretion in DOC2B^wt is larger than EGFP control and DOC2B^D218,220N cells.