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Proton transport and membrane shuttling in turtle bladder epithelium
The Journal of Membrane Biology
|January 1, 1986
Summary
Proton pumps in turtle bladders regulate transport by altering apical membrane area. Acetazolamide (AZ) affects this process, impacting proton secretion and membrane dynamics, suggesting pump kinetics also play a role.
Area of Science:
- Cell biology
- Renal physiology
- Membrane transport
Background:
- Proton secretion in turtle bladders relies on proton pumps in carbonic-anhydrase (CA)-rich cells.
- Regulation of proton transport may involve changes in apical membrane area via endocytosis and exocytosis.
Purpose of the Study:
- To investigate the role of endocytotic and exocytotic processes in regulating proton transport.
- To quantify the effects of acetazolamide (AZ) on apical membrane area and proton transport rates.
Main Methods:
- Transepithelial impedance analysis to estimate membrane area changes.
- Electron microscopy to visualize endocytotic vesicles.
- Fluorescent marker uptake to measure endocytosis rates.
Main Results:
- Endocytosis and exocytosis occur in CA-rich cells.
- Acetazolamide (AZ) treatment reduced apical membrane area and proton transport.
- Proton transport decline was not solely proportional to membrane area reduction, indicating altered pump kinetics.
- CA-rich cells show constitutive pinocytosis, independent of transport rate.
- AZ transiently increased endocytosis and membrane shuttling.
Conclusions:
- Proton transport regulation involves both apical membrane area changes and pump kinetics.
- Acetazolamide (AZ) influences a regulated endocytotic pathway distinct from constitutive pinocytosis.