[Structural and functional characteristics of the cellular reaction of the bladder epithelium in the frog to calcium extraction from the apical and basolateral membranes].

Extraction of Ca++ ions from cells of the frog urinary bladder serosa side is followed by an increase in the bladder wall permeability for water and inulin. Ultrastructural changes were observed, such as destruction of cell junctions, swelling of the cell and their organelles, reconstruction of the cytoskeleton elements. The free calcium Ringer solution injected in the bladder lumen does not change the permeability of the wall for water and sodium ions. In this case the cell response to the antidiuretic hormone decreases; the ultrastructure of cells and intercellular junctions is not disturbed; the distribution of intramembrane particles on the P- and E-faces of the apical membrane is normal. The above results indicate that there are qualitative differences in the cell response towards the extraction of Ca++-ions between the serosal and mucosal membranes. This also suggests that on the external surface of the apical membrane Ca++ ions may play a very important role in redistribution of intramembrane particles under the action of the antidiuretic hormone.