Ultrastructural aspects of membrane fusion

With the availability of a new technique, the freeze fracture, freeze etch technique, it became possible to localize internal membrane components at specific sites. It now became possible to attack directly several vital links in the chain of events leading to release of a secretory product. There are two ways in which secretory product release might take place. The first is independent of membrane fusion while in the second membrane fusion is imperative for release. In both postulates, release is dependent on formation of ion permeability channels through the hydrophobic centers of the membranes.