Cyclic AMP increases electrical capacitance of apical membrane of toad urinary bladder
1Laboratorium voor Fysiologie, KUL, Leuven, Belgium.
Summary
Cyclic AMP (cAMP) increases toad bladder apical membrane area, suggesting it acts as a second messenger. Oxytocin and other cAMP-elevating agents promote exocytotic vesicle fusion with the apical membrane.
Area of Science:
- Physiology
- Cell Biology
- Membrane Biology
Background:
- Oxytocin is known to affect water and solute transport in amphibian bladders.
- The role of cyclic AMP (cAMP) as a second messenger in these processes is under investigation.
- Understanding the mechanisms of apical membrane regulation is crucial for bladder function.
Purpose of the Study:
- To investigate the effects of oxytocin and cAMP-elevating agents on toad urinary bladder impedance.
- To determine if changes in membrane capacitance are linked to apical membrane area.
- To elucidate the role of cAMP in regulating apical membrane dynamics.
Main Methods:
- Transepithelial impedance measurements using a computerized sine wave method.
- Calculation of membrane capacitance from impedance data.
- Application of oxytocin, chlorophenyl-thio-cyclic AMP, forskolin, and theophylline to toad urinary bladders.
Main Results:
- Oxytocin, chlorophenyl-thio-cyclic AMP, forskolin, and theophylline all increased tissue capacitance.
- Increased tissue capacitance is proportional to apical membrane area in these tissues.
- These findings indicate an expansion of the apical membrane surface.
Conclusions:
- Cyclic AMP (cAMP) acts as a second messenger in the action of oxytocin and other tested agents.
- cAMP mediates the fusion of exocytotic vesicles with the apical membrane.
- This mechanism contributes to the regulation of apical membrane area in the toad urinary bladder.
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