Membrane interactions between adjacent mucols secretion granules

In primate goblet cells, the membranes of adjacent mucous granules from contact areas which appear as extensive pentalaminar fusion sites in thin sections. In freeze-fracture replicas, the same membrane areas are smooth, except for a few 6-8-nm particles which adhere to the E face. These protein-poor membrane interaction sites are relatively long- lived, and it is proposed that further stimulus may be required to trigger membrane fission.