Intermediates in the constitutive and regulated secretory pathways released in vitro from semi-intact cells

Secretogranin II, a marker for the regulated secretory pathway, was also quantified in the experiments described above. After a 5-min pulse labeling, there .was an ATP-dependent release of secretogranin II-containing vesicles from the permeabilized cells during the in vitro incubation (Fig . 7 A) . In contrast to proteoglycans, most of the secretogranin II was broadly distributed across the velocity gradients with a much greater fraction (55-85%) in more rapidly sedimenting membranes . After equilibrium centrifugation the regulated secretory marker was found in vesicles more dense than the proteoglycan-containing constitutive secretory vesicles ( Fig . 1 .06 1 .1 1 .14 1 .18 1 .22 1 .26 equilibrium density