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Electrical transients produced by the toad urinary bladder in response to altered medium osmolality
1Department of Physiology, University of Otago Medical School, Dunedin, New Zealand.
The Journal of Physiology
|December 1, 1988
Summary
Changes in serosal fluid osmolality significantly alter toad bladder current, while mucosal changes do not. These osmotic responses are cellular, involve ion gradients and sodium pump activity, and can exhibit oscillations.
Area of Science:
- Physiology
- Renal Physiology
- Electrophysiology
Background:
- Transepithelial current in the toad urinary bladder is crucial for ion transport.
- Understanding the regulation of this current by osmotic changes is vital for renal physiology.
Purpose of the Study:
- To investigate the effects of altered media osmolality on transepithelial current in the toad urinary bladder.
- To elucidate the mechanisms underlying osmotic responses, including cellular origin and ion transport involvement.
Main Methods:
- Voltage-clamp techniques were applied to toad urinary bladders.
- Changes in mucosal and serosal fluid osmolality were systematically varied.
- Amiloride was used to block active current, and ion substitutions (gluconate) were performed.
Main Results:
- Serosal fluid osmolality changes significantly altered transepithelial current, while mucosal changes had no effect.
- Responses were proportional to osmotic steps, reproducible, and reversible within a specific osmolality range.
- Amiloride blocked these responses, indicating a cellular origin, and oscillations were observed in transient currents.
Conclusions:
- Osmotic steps in serosal fluid initiate ion gradient changes and alter sodium pump activity.
- A voltage-dependent sodium conductance in the apical membrane is suggested.
- The study highlights the sensitivity of toad bladder electrophysiology to serosal osmotic environment.