The ultrastructure of the vacuolar system of the frog urinary bladder epithelium has been studied under the influence of an antidiuretic hormone (ADH). It has been shown that large vacuoles of irregular form appear during the water stimulation. In some cases, the vacuole reservoirs are continuous with the electron dense canaliculi localized predominantly in the apical part of the cell cytoplasm. Vacuole membranes, microtubules and microfilaments are tightly connected. These cytoskeleton elements are supposed to be involved in the change of the vacuole form. During the incubation of the bladder in hypotonic solutions without ADH and osmotic gradient, swelling of all cell types was observed accompanied with the appearance of small vacuoles in the cytoplasm. Thus, it has been supposed that the formation of large vacuoles in the granular cells may be associated with the increased water transport across the cell stimulated by ADH.
Animals Epithelium