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Evaluation of granule exocytosis in toad urinary bladder
The American Journal of Physiology
|September 1, 1986
Summary
Phorbol myristate acetate (PMA) triggers exocytosis of granules in toad bladder cells. However, these granules are not essential for vasopressin-induced water permeability changes.
Area of Science:
- Cell biology
- Epithelial physiology
Background:
- Toad urinary bladder epithelial cells possess apical granules.
- Phorbol myristate acetate (PMA) induces exocytosis of these granules.
- PMA also increases epithelial water permeability, suggesting a role for granules.
Purpose of the Study:
- To investigate the role of granule exocytosis in mediating vasopressin-induced water permeability in toad urinary bladder epithelial cells.
Main Methods:
- Electron microscopic immunolocalization to identify granule components.
- Competitive immunoassay using antibodies against a 70-kDa apical glycocalyx protein.
- Stimulation of toad urinary bladder epithelial cells with PMA and vasopressin.
Main Results:
- PMA induced a fourfold increase in antigen release and doubled apical surface antigen.
- Serosal PMA or inactive phorbol didecanoate did not induce significant antigen release.
- Vasopressin stimulation did not show a detectable change in granule exocytosis.
Conclusions:
- Granule exocytosis is induced by mucosal PMA but is not a significant mediator of vasopressin-induced water permeability changes in toad urinary bladder epithelial cells.