Cellular changes in the toad urinary bladder in response to metabolic acidosis

Area of Science:

• Physiology
• Cell Biology
• Comparative Anatomy

Background:

• The toad urinary bladder is a model for studying epithelial transport.
• Mitochondria-rich (MR) cells are known to mediate H+ excretion.
• The bladder's response to metabolic acidosis is not fully understood at the cellular level.

Purpose of the Study:

• To investigate changes in MR cell populations within the toad bladder during metabolic acidosis.
• To correlate cellular adaptations with functional changes in H+ excretion.

Main Methods:

• Metabolic acidosis was induced in Bufo marinus.
• Urinary bladders were isolated and mounted for H+ excretion measurements.
• Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to quantify and identify cell types.

Main Results:

• Toads with metabolic acidosis exhibited a higher ratio of MR cells to granular cells compared to normal toads.
• H+ excretion was elevated in bladders from acidotic toads.
• SEM and TEM confirmed an increased abundance of MR cells.

Conclusions:

• Metabolic acidosis stimulates an increase in the number of MR cells in the toad urinary bladder.
• This cellular adaptation enhances the bladder's capacity for acid excretion, aiding in acid-base homeostasis.