AJP - Cell Physiology, Vol 244, Issue 5 309-C312, Copyright © 1983 by American Physiological Society
Release of chromaffin granular content on interaction with plasma membranes
F. Konings, B. Majchrowicz and W. De Potter
Cell-free interaction between bovine adrenal medullary plasma membranes and
chromaffin granules results in the release of the granular content, a
process specifically controlled by micromolar concentrations of calcium and
therefore regarded as a putative model for exocytosis. The density gradient
distribution of interacted organelles (1 min at 37 degrees C) was compared
with the distribution of noninteracted material (kept at 0 degree C).
Self-generating Percoll gradients, in which intact chromaffin granules were
separated from plasma membranes and empty granule "ghosts," were used. The
plasma membrane-induced release of the chromaffin granular matrix upon
concomitant incubation was demonstrated by the disappearance of the "intact
granule" peak accompanied by a proportional rise of the "granule ghost"
peak. The degree of granule disappearance depended on the amount of plasma
membranes added. The soluble content of the fraction that had disappeared
was dispersed throughout the gradient. No shift of the granule peak toward
intermediate densities was observed; this suggests that the loss of each
granule's content is an all-or-none phenomenon rather than a partial
release.
