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Vasoactive intestinal peptide stimulates alkali excretion in turtle urinary bladder
Vasoactive intestinal peptide (VIP) stimulates alkali secretion in turtle bladders, acting as a hormonal regulator. This process involves cyclic AMP (cAMP) and enhances alkali excretion.
Area of Science:
- Physiology
- Urology
- Comparative Biology
Background:
- The turtle urinary bladder actively secretes alkali via an electrogenic transport mechanism.
- This secretion is stimulated by cyclic AMP (cAMP) and is more pronounced in alkalotic turtles.
Purpose of the Study:
- To investigate the role of vasoactive intestinal peptide (VIP) in regulating alkali secretion in the turtle urinary bladder.
- To elucidate the signaling pathway involved in VIP-mediated alkali excretion.
Main Methods:
- Addition of VIP to the serosal side of isolated turtle urinary bladders.
- Measurement of alkali secretion and short-circuit current.
- Assessment of VIP effects in the presence and absence of a phosphodiesterase inhibitor.
- Administration of a cAMP analog after VIP stimulation.
Main Results:
- Serosal VIP addition rapidly increased both alkali secretion and short-circuit current.
- VIP-induced alkali secretion was enhanced by a phosphodiesterase inhibitor.
- Subsequent addition of a cAMP analog did not further increase alkalinization, suggesting VIP acts upstream in the cAMP pathway.
Conclusions:
- VIP acts as a hormonal up-regulator of alkali excretion in the turtle urinary bladder.
- VIP-induced alkali secretion is mediated through the cyclic AMP (cAMP) signaling pathway.
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