Organic cation secretion by Cancer borealis urinary bladder

Area of Science:

• Marine biology
• Comparative physiology
• Renal physiology

Background:

• The model organic cation tetraethylammonium (TEA) serves as a probe for studying renal transport mechanisms.
• Previous studies indicated a potent renal excretory system in the crab Cancer borealis.

Purpose of the Study:

• To investigate the mechanisms of tetraethylammonium (TEA) transport in the urinary bladder of Cancer borealis.
• To characterize the cellular and molecular pathways involved in TEA secretion and reabsorption.

Main Methods:

• Clearance studies were performed to measure TEA excretion rates.
• Uptake studies using urinary bladder slices assessed TEA transport kinetics.
• Flux measurements in mounted bladders quantified secretory and reabsorptive fluxes.
• Inhibitor studies with quinine and N1-methylnicotinamide chloride were conducted.

Main Results:

• Cancer borealis demonstrated a potent renal excretory system for TEA, with clearance significantly exceeding polyethylene glycol clearance.
• Urinary bladder uptake of TEA was concentrative, saturable, and dependent on glycolysis.
• Bladders exhibited a large net secretory flux for TEA, with a high secretory to reabsorptive flux ratio.
• Secretory transport was concentrative and sensitive to quinine, while reabsorptive transport was not.

Conclusions:

• The urinary bladder of Cancer borealis employs a transcellular pathway for TEA transport, mediated by carriers at both serosal and luminal membranes.
• This study elucidates the complex transport mechanisms of organic cations in marine invertebrates, providing insights into renal function.
• Similar TEA secretion mechanisms were observed in Cancer irroratus and Homarus americanus, suggesting conserved pathways in crustaceans.