title: Cytochalasin B inhibition of toad bladder apical membrane responses to ADH.
abstract: The possible role of actin microfilaments in antidiuretic hormone (ADH)-induced increases in apical membrane water permeability was investigated in studies that evaluate inhibition by cytochalasin B of both permeability and membrane structural responses in the toad urinary bladder. Experiments were carried out in the absence of a transepithelial osmotic gradient to eliminate possible flow-induced distortions of the response. Measurements of osmotic water permeability after a brief tissue fixation with glutaraldehyde show that cytochalasin B reduces the permeability response to ADH by approximately one-third. Freeze-fracture electron microscopy indicates that the intramembrane particle aggregates, previously found to correlate closely with ADH-induced permeability, are reduced by about the same extent (28%) under these conditions. However, the frequency of apical membrane fusion events was not affected by cytochalasin B treatment. These results suggest that cytochalasin B treatment in the absence of an osmotic gradient alters the ADH-induced permeability through an effect on apical membrane aggregate frequency.
mesh_terms: D000818:Animals; D002024:Bufo marinus; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003571:Cytochalasin B / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D012016:Reference Values; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*; D014667:Vasopressins / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D014667:Vasopressins; D003571:Cytochalasin B