Nature of ADH-Induced Endosomes In Toad Urinary Bladder Granular Epithelial Cells

Abstract

Serosal ADH stimulation enhances water flow under an imposed osmotic gradient through insertion of water channels (aggrephores) into the mucosal plasma membrane of toad urinary bladder sacs. Following cessation of ADH actions, water channels are retrieved as endosomes that can be visualized by mucosal inclusion of horseradish peroxidase (HRP) into round vesicles, long tubules and multivesicular bodies within the cytosol (1,2,3). Endosomes also occur adjacent to golgi bodies or lysosomes (1,2,3). However, true nature of endosomes including their formation at the mucosal surface and their shuttling in granular cells is still unclear (4,5). Current studies were undertaken to understand the role of endosomes in water channel cycling in this renal membrane model.Urinary bladder sacs removed surgically from doubly-pithed toads, were suspended at ends of glass tubes. Control (no hormone) and experimental bladder sacs were exposed to ADH for 10 min in the absence of osmotic gradient.