Cytochalasin D suppresses beta-adrenergic induced protein discharge without inhibiting membrane fusion.

Biochemical studies have shown that low doses of Cytochalasin D (CD) inhibit protein discharge evoked by isoproterenol, a beta-adrenergic inducer, in isolated lobules of Rat parotid gland. Ultrastructural and radioautographic studies reported here indicate that, when lobules are treated by CD before isoproterenol stimulation, the connection of secretory granules with the acinar lumen is indeed prevented, but fusion of membrane granules evoked by isoproterenol still occurs. This fusion takes place with vacuoles induced by CD and possibly with other granules.