Abstract
A secretory granular fraction (SG) and a plasma membrane rich fraction (PM) have been isolated from rat parotid gland by differential and Percoll gradient centrifugation. With these two fractions, a cell-free interaction system has been reconstituted to clarify the exocytotic between the secretory granules and plasma membranes, and the conditions of amylase release from SG have been characterized in vitro. The addition of PM into this assay system induced a rapid and transient release of amylase from SG. Some other membranes such as erythrocyte ghosts also mimicked the effect of PM. This release was increased by Ca 2+, but was not completely blocked by EGTA. Simultaneous addition of 1 mM ATP with 1 mM MgCl 2 (Mg-ATP) inthe presence of Ca 2+ reduced this release. However, in spite of the existence of Mg-ATP, the stimulation of PM-induced amylase release was caused by Ca 2+ in a concentration-dependent manner (10 −7-10 −3M). These results suggest that Ca 2+ and Mg-ATP should participate as important regulators in the exocytotic interaction between secretory granules and plasma membranes in this system. Furthermore, the differences between our system and intact cells are also discussed.
Published Version
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