title: Actin filaments and vasopressin-stimulated water flow in toad urinary bladder.
abstract: Vasopressin increases the water permeability of the apical membrane of the granular epithelial cells of the toad urinary bladder. Cytochalasin B inhibits this action of the hormone, indicating that microfilaments may play a role in the water permeability response. We have extended previous functional studies with cytochalasin B and have demonstrated that dihydrocytochalasin B, a more specific inhibitor of actin filament elongation, similarly diminishes the hydrosmotic response to vasopressin. Biochemical studies of isolated epithelial cells indicate that an actin-like protein accounts for about 10% of the soluble protein of the epithelium. Morphological studies of whole toad bladders incubated with heavy meromyosin conclusively demonstrate that actin is a component of the epithelial cells and that actin-containing filaments are associated with both plasma membranes and cytoplasmic organelle membranes. Taken together, these findings provide strong, albeit indirect, evidence that actin microfilaments play a functional role in the hormone-induced increase in water permeability in the toad urinary bladder.
mesh_terms: D000199:Actins / Q000302:isolation & purification / Q000502:physiology*; D000818:Animals; D001834:Body Water / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D004848:Epithelium / Q000648:ultrastructure; D005260:Female; D007700:Kinetics; D008854:Microscopy, Electron; D008871:Microvilli / Q000648:ultrastructure; D009092:Mucous Membrane / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*; D014667:Vasopressins / Q000502:physiology*
chemical_list: D000199:Actins; D014667:Vasopressins; D003571:Cytochalasin B; D000242:Cyclic AMP