Module 7: Figure chromaffin cell exocytosis
Two modes of chromaffin cell Ca2+-dependent exocytosis.
Release of chromaffin granules occurs through either a kiss-and-run mechanism or through a classical exocytotic/endocytotic cycle. The former mechanism, which is triggered by low levels of Ca2+, creates a small fusion pore that can rapidly reverse, resulting in a small release of small molecules such as adrenaline. At higher levels of Ca2+, a full fusion event occurs, resulting in the releases of both small molecules and the larger molecules in the granule, such as the opiates and chromogranin. This exocytosis is then followed by the membrane retrieval process of endocytosis (see Module 4: Figure vesicle cycle).