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Published on: August 24, 2021
Amiloride-sensitive sodium absorption is different in vertebrates and invertebrates
Katja Sobczak1, Anne Willing, Kristina Kusche
1Institute of Animal Physiology, Westphalian Wilhelms-University Muenster, Hindenburgplatz 55, D-48143 Muenster, Germany.
Summary
Amiloride-sensitive sodium (Na+) absorption in leech skin differs functionally and structurally from vertebrate epithelial Na+ channels (ENaC). This invertebrate Na+ transport is mediated by a novel protein, lENaTP, not ENaC.
Area of Science:
- Comparative physiology
- Ion transport mechanisms
- Invertebrate biology
Background:
- Amiloride-sensitive sodium (Na+) absorption is crucial in vertebrate epithelia.
- Little is known about invertebrate amiloride-sensitive Na+ absorption.
- Vertebrate Na+ absorption is primarily mediated by the epithelial Na+ channel (ENaC).
Purpose of the Study:
- To compare vertebrate and invertebrate amiloride-sensitive Na+ absorption.
- To investigate the mechanism of Na+ absorption in the leech Hirudo medicinalis.
- To identify potential invertebrate counterparts to vertebrate ENaC.
Main Methods:
- Electrophysiological analysis using modified Ussing chambers.
- Molecular techniques including cDNA library construction and PCR.
- Biochemical assays to test channel blockers and effectors.
Main Results:
- Leech integument Na+ transport was unaffected by trypsin, unlike vertebrate ENaC.
- Protons, Ni2+, and Zn2+ reduced leech Na+ currents, contrasting with ENaC activation.
- No ENaC-like sequences were found in the leech using molecular approaches.
Conclusions:
- Amiloride-sensitive Na+ absorption in leeches is not mediated by ENaC.
- A novel invertebrate protein, leech epithelial Na+ transporting protein (lENaTP), is responsible for this transport.
- lENaTP represents a distinct member of the ENaC/DEG channel family.
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