Effect of vasopressin and serosal hypertonicity on toad urinary bladder

Area of Science:

• Cell biology
• Physiology
• Electron microscopy

Background:

• The toad urinary bladder's granular cell surface exhibits a ridge-like pattern.
• Vasopressin (VP) is known to influence toad bladder physiology.

Purpose of the Study:

• To investigate the cellular mechanisms behind vasopressin-induced surface changes in toad urinary bladder granular cells.
• To determine if osmotic water movement or cell swelling is required for VP-induced microvillus formation.
• To explore the role of cyclic AMP (cAMP) and other stimuli in altering granular cell surface morphology.

Main Methods:

• Scanning electron microscopy was used to examine the mucosal surface of toad urinary bladders.
• Tissues were exposed to various stimuli: vasopressin (VP), 8-bromo-cAMP, acetylcholine chloride, hypertonic, and hypotonic solutions.
• Cellular responses were observed under different osmotic conditions and after specific chemical exposures.

Main Results:

• Vasopressin (VP) and 8-bromo-cAMP induced microvillus formation on granular cells, independent of osmotic water flow or cell swelling.
• Acetylcholine chloride did not induce microvilli but altered apical surface convexity.
• Serosal hypertonicity also induced microvilli formation, similar to VP, but via an undefined mechanism.

Conclusions:

• Transepithelial osmotic water flow and cell swelling are not required for VP-induced microvillus formation.
• The VP response is likely mediated by the generation of cyclic AMP (cAMP).
• Serosal hypertonicity induces similar surface changes through a distinct, yet to be determined, pathway.