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Characteristics of toad bladder urinary acidification
J E Silveira1, S E Perez, B R Cirne
1Departamento de Ciências da Saúde (Fisiologia), Universidade Federal de São Carlos, Brasil.
Summary
The toad bladder actively acidifies urine, similar to turtle bladders. Increased CO2 or lower cell pH enhances proton secretion, indicating a regulated urinary acidification system.
Area of Science:
- Physiology
- Comparative Biology
- Urology
Background:
- The urinary acidification system in toad bladders is crucial for maintaining acid-base balance.
- Previous studies on bladder acidification have primarily focused on turtle bladders.
Purpose of the Study:
- To investigate the urinary acidification system in the toad bladder (Bufo marinus ictericus).
- To characterize the factors influencing proton secretion and the electrical properties of the toad bladder epithelium.
Main Methods:
- Utilized an improved technique for mounting bladder membranes between lucite half chambers.
- Measured acidification rates and proton secretion (JH) under various conditions, including ouabain treatment, CO2 exposure, and altered cell pH.
- Assessed passive proton permeability and proton-motive force (PMF') across the epithelium.
Main Results:
- Ouabain-treated toad bladders showed acidification rates comparable to turtle bladders in the absence of exogenous CO2.
- Proton secretion (JH) increased with the addition of 1% CO2 to the serosal gas phase.
- Decreasing cell pH by salicylic acid also stimulated JH, while luminal membrane depolarization increased JH without altering PMF'.
Conclusions:
- The toad bladder possesses a functional urinary acidification system regulated by CO2 and cell pH.
- Passive proton permeability and proton-motive force are similar to those observed in turtle bladders.
- The electrical potential difference across the luminal membrane is negligible under specific conditions, suggesting a key role in regulating proton secretion.