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Sulfate transport mechanisms in epithelial systems
G A Gerencser1, G A Ahearn, J Zhang
1Department of Physiology, College of Medicine, University of Florida, Gainesville, Florida 32610, USA. gag@phys.med.ufl.edu
The Journal of Experimental Zoology
|March 10, 2001
Summary
Lobsters utilize a novel chloride-sulfate exchange mechanism in their digestive glands for sulfate secretion. This electrogenic process involves distinct transporters in the hepatopancreas, influencing hemolymph sulfate levels.
Area of Science:
- Invertebrate physiology
- Gastrointestinal transport
- Ion exchange mechanisms
Background:
- The hepatopancreas in lobsters (Homarus americanus) separates the gut lumen from hemolymph.
- Understanding invertebrate digestive processes is crucial for comparative physiology.
Purpose of the Study:
- To elucidate the mechanism of chloride-sulfate exchange in the lobster hepatopancreas.
- To identify the specific transport systems involved in transcellular sulfate secretion.
Main Methods:
- Isolation and characterization of brush border and basolateral membrane vesicles.
- Investigation of transporter activity using ion gradients and stimulation factors.
Main Results:
- A high-affinity, proton-stimulated, electrogenic chloride-sulfate antiport system was identified at the luminal membrane.
- An electroneutral, oxalate-responsive basolateral antiport system was also characterized.
- No sodium-sulfate co-transport was observed, differing from vertebrate models.
Conclusions:
- The identified antiport systems explain low hemolymph sulfate levels in decapod crustaceans.
- Electrogenic chloride-antiport facilitates sulfate secretion in invertebrates, potentially adapted to marine environments.