[The electron microscopic analysis of the mechanism of the insertion of high water permeability domains into the apical membrane of epithelial cells].

Fusion processes of cell organelles with granular cell apical membranes under ADH-induced water permeability has been analysed. The data obtained suggest that specific granule membranes inserted in the apical membrane may change its water permeability. This occurs due to the fusion of the granule membrane with the apical membrane without exocytosis, the granule contents remaining in the cytoplasm.