Figure 8.

Effects of multiple stimulations on HRP activity in SLMVs. Five 10-cm dishes were plated with PC12 cells transfected to express ssHRP^P-selectin, left for 3 d, and then incubated with ³H-dopamine for 2 h. One dish was left unstimulated (control; panel 1), one dish was stimulated for 5 min and then left for 30 min (stimulate, + 30 min; panel 2), one dish was treated as in panel 2 and then stimulated again for 5 min (stimulate, + 30 min, stimulate; panel 3), one dish was treated as in panel 3 and then allowed to recover for 30 min (simulate, + 30 min, stimulate, + 30 min; panel 4), and one dish was treated as in panel 4 and then stimulated for a third time for 5 min (stimulate, + 30 min, stimulate, + 30 min, stimulate; panel 5). Each dish was then fractionated and HRP activity in fractions from a glycerol gradient was measured in triplicate. Means of determinations are shown; error bars indicate the SD for that experiment. Interexperimental variation is detailed in the text. The bar graph under each panel indicates the amount of ³H-dopamine released during the last 5-min stimulation of the procedure carried out on that dish.