scholarly journals Role of osmotic forces in exocytosis: studies of ADH-induced fusion in toad urinary bladder.

1981 ◽  
Vol 91 (2) ◽  
pp. 584-588 ◽  
Author(s):  
W A Kachadorian ◽  
J Muller ◽  
A Finkelstein
Keyword(s):  
Plasma Membrane ◽  
Urinary Bladder ◽  
Antidiuretic Hormone ◽  
Basic Mechanism ◽  
Toad Urinary Bladder ◽  
Bathing Medium ◽  
Intramembrane Particle ◽  
Luminal Membrane ◽  
Particle Aggregates

Antidiuretic hormone (ADH) treatment of toad urinary bladder activates an exocytotic-like process by which intramembrane particle aggregates are transferred from membranes of elongated cytoplasmic tubules to the luminal-facing plasma membrane. We find that the number of these ADH-induced fusion events, and the number of aggregates appearing in the luminal membrane, are reduced when the luminal bathing medium is made hyperosmotic. As an apparent consequence of the inhibition of their fusion with the luminal membrane, the elongated cytoplasmic tubules become enormously swollen into large, rounded vesicles. These results are consistent with the view that osmotic forces are essential to the basic mechanism of exocytosis.

scholarly journals Evidence that ADH-stimulated intramembrane particle aggregates are transferred from cytoplasmic to luminal membranes in toad bladder epithelial cells.

1980 ◽  
Vol 85 (1) ◽  
pp. 83-95 ◽  
Author(s):  
J Muller ◽  
W A Kachadorian ◽  
V A DiScala
Keyword(s):  
Urinary Bladder ◽  
Freeze Fracture ◽  
Toad Urinary Bladder ◽  
Granular Cells ◽  
Thin Sections ◽  
Intramembrane Particle ◽  
Luminal Membrane ◽  
Particle Aggregates ◽  
Cytoplasmic Structures ◽  
Induced Changes

In freeze-fracture (FF) preparations of ADH-stimulated toad urinary bladder, characteristic intramembrane particle (IMP) aggregates are seen on the protoplasmic (P) face of the luminal membrane of granular cells while complementary parallel grooves are found on the exoplasmic (E) face. These IMP aggregates specifically correlate with ADH-induced changes in water permeability. Tubular cytoplasmic structures whose membranes contain IMP aggregates which look identical to the IMP aggregates in the luminal membrane have also been described in granular cells from unstimulated and ADH-stimulated bladders. The diameter of these cytoplasmic structures (0.11 +/- 0.004 micrometers) corresponds to that of tubular invaginations of the luminal membrane seen in thin sections of ADH-treated bladders (0.13 +/- 0.005 micrometers). Continuity between the membranes of these cytoplasmic structures (which are not granules) and the luminal membrane has been directly observed in favorable cross-fractures. In FF preparations of the luminal membrane, these apparent fusion events are seen as round, ice-filled invaginations (0.13 +/- 0.01 micrometer Diam), of which about half have the characteristic ADH-associated aggregates near the point of membrane fusion. They are less numerous than, but linearly related to, the number of aggregates counted in the same preparations (n = 78, r = 0.71, P less than 0.01). These observations suggest that the IMP aggregates seen in luminal membrane after ADH stimulation are transferred preformed by fusion of cytoplasmic with luminal membrane.

The role of sodium-channel density in the natriferic response of the toad urinary bladder to an antidiuretic hormone

1982 ◽  
Vol 64 (1-2) ◽  
pp. 77-89 ◽  
Author(s):  
Jack H. Y. Li ◽  
Lawrence G. Palmer ◽  
Isidore S. Edelman ◽  
Bernd Lindemann
Keyword(s):  
Urinary Bladder ◽  
Sodium Channel ◽  
Antidiuretic Hormone ◽  
Toad Urinary Bladder ◽  
Channel Density

ADH or theophylline-induced changes in intracellular free and membrane-bound calcium

1984 ◽  
Vol 247 (6) ◽  
pp. F939-F945 ◽  
Author(s):  
R. M. Burch ◽  
P. V. Halushka
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Urinary Bladder ◽  
Antidiuretic Hormone ◽  
Water Permeability ◽  
Time Course ◽  
Toad Bladder ◽  
Toad Urinary Bladder ◽  
Membrane Bound ◽  
Induced Changes

Ca2+ is thought to play a role in the enhancement of water permeability of toad urinary bladder epithelial cells by antidiuretic hormone (ADH) or theophylline. This study examined the effects of ADH and theophylline on intracellular free Ca2+ ([Ca2+]i) and total cellular exchangeable Ca2+ in isolated toad bladder epithelial cells. ADH or theophylline enhanced water permeability maximally by 15-25 min after a 4-min lag. 45Ca2+ efflux, a probe for total cellular exchangeable (plasma membrane plus intracellular) Ca2+, was enhanced by ADH within 2 min and returned to control by 8 min. Chlortetracycline fluorescence, a probe for intracellular Ca2+ only, was not affected, suggesting that ADH released only plasma membrane-bound Ca2+. Theophylline enhanced 45Ca2+ efflux and decreased chlortetracycline fluorescence, suggesting release of Ca2+ from intracellular sources. Both agents decreased [Ca2+]i as assessed by quin-2 fluorescence with a time course similar to the enhancement in water permeability. The results suggest that the changes in membrane-bound Ca2+ and [Ca2+]i induced by ADH and theophylline may play a role in the enhanced permeability to water in response to these agents.

Role of PKC isozymes in water transport in toad urinary bladder

1991 ◽  
Vol 49 ◽  
pp. 302-303
Author(s):  
A.J. Mia ◽  
L.X. Oakford ◽  
T. Yorio
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Membrane Surface ◽  
Protein A ◽  
Cell Types ◽  
Leukemic Cells ◽  
Toad Urinary Bladder ◽  
Pkc Isozymes ◽  
Antibody Labeling

Protein kinase C (PKC) isozymes, when activated, are translocated to particulate membrane fractions for transport to the apical membrane surface in a variety of cell types. Evidence of PKC translocation was demonstrated in human megakaryoblastic leukemic cells, and in cardiac myocytes and fibroblasts, using FTTC immunofluorescent antibody labeling techniques. Recently, we reported immunogold localizations of PKC subtypes I and II in toad urinary bladder epithelia, following 60 min stimulation with Mezerein (MZ), a PKC activator, or antidiuretic hormone (ADH). Localization of isozyme subtypes I and n was carried out in separate grids using specific monoclonal antibodies with subsequent labeling with 20nm protein A-gold probes. Each PKC subtype was found to be distributed singularly and in discrete isolated patches in the cytosol as well as in the apical membrane domains. To determine if the PKC isozymes co-localized within the cell, a double immunogold labeling technique using single grids was utilized.

Cloning of an aquaporin homologue present in water channel containing endosomes of toad urinary bladder

1996 ◽  
Vol 270 (1) ◽  
pp. C372-C381 ◽  
Author(s):  
J. Siner ◽  
A. Paredes ◽  
C. Hosselet ◽  
T. Hammond ◽  
K. Strange ◽  
...  
Keyword(s):  
Urinary Bladder ◽  
Water Channel ◽  
Structural Features ◽  
Xenopus Laevis Oocytes ◽  
Sequence Motif ◽  
Toad Urinary Bladder ◽  
Cytoplasmic Vesicles ◽  
Terrestrial Habitats ◽  
Total Body

Regulation of total body water balance in amphibians by antidiuretic hormone (ADH) contributed to their successful colonization of terrestrial habitats approximately 200-300 million years ago. In the mammalian kidney, ADH modulates epithelial cell apical membrane water permeability (Pf) by fusion and retrieval of cytoplasmic vesicles containing water channel proteins called aquaporins (AQPs). To determine the role of AQPs in ADH-elicited Pf in amphibians, we have identified and characterized a unique AQP from Bufo marinus called AQP toad bladder (AQP-TB). AQP-TB possesses many structural features common to other AQPs, AQP-TB is expressed abundantly in ADH-responsive tissues, including toad urinary bladder and skin as well as lung, skeletal muscle, kidney, and brain. In a manner identical to that reported for the mammalian ADH-elicited water channel AQP2, AQP-TB expression is increased significantly by intervals of dehydration or chronic ADH stimulation. However, expression of AQP-TB protein in Xenopus laevis oocytes does not significantly increase oocyte Pf. The lack of expression of functional AQP-TB water channels in oocytes may result from intracellular sequestration of AQP-TB due to the presence of a YXRF sequence motif present in its carboxyterminal domain.

Fluorescent markers to study membrane retrieval in antidiuretic hormone-treated toad urinary bladder

1986 ◽  
Vol 251 (2) ◽  
pp. C274-C284 ◽  
Author(s):  
H. W. Harris ◽  
J. B. Wade ◽  
J. S. Handler
Keyword(s):  
Electron Microscopy ◽  
Urinary Bladder ◽  
Horseradish Peroxidase ◽  
Antidiuretic Hormone ◽  
Apical Membrane ◽  
Granular Cell ◽  
Cell Uptake ◽  
Toad Urinary Bladder ◽  
Osmotic Gradient ◽  
Apical Surface

Antidiuretic hormone (ADH) stimulation of toad urinary bladder causes fusion of intracellular vesicles called aggrephores with the apical plasma membrane of granular cells. Aggrephores contain intramembrane particle aggregates whose appearance in the apical membrane is believed to produce a large increase in its water permeability. ADH removal (ADH washout) is thought to cause the retrieval of aggrephores into granular cell cytoplasm. We studied granular cell uptake of dextran and horseradish peroxidase conjugated with fluorescein, rhodamine, or both during ADH washout. Granular cell uptake of fluorescent dextran was dependent on prior exposure to ADH, a linear function of dextran concentration, and increased by a transepithelial osmotic gradient. Immediately after removal of ADH, granular cell fluorescence was finely dispersed and located near the apical surface. Subsequently, it coalesced into larger bodies. This change was most apparent when a single bladder was subjected to two cycles of ADH stimulation and removal using a dextran containing a different fluorophore for each cycle. The ultrastructural correlate for these fluorescent patterns was identified using rhodamine-labeled horseradish peroxidase. Electron microscopy showed that after detachment from the apical membrane, label was initially in tubular-shaped vesicles near the apical surface. Later, these vesicles clustered near multivesicular bodies and transferred their label to these structures. These tubular vesicles closely resemble the morphology of aggrephores visualized by freeze-fracture electron microscopy. We conclude that these fluorescent compounds can be used as markers for the luminal contents of membrane retrieved during ADH washout and allow detailed study of its intracellular processing.

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