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Rabbit proximal colon: a distinct transport epithelium
The American Journal of Physiology
|May 1, 1984
Summary
Rabbit proximal colon exhibits unique ion transport, featuring epinephrine-stimulated sodium-chloride absorption distinct from distal colon. Secretory stimuli paradoxically reduce absorption rather than induce secretion.
Area of Science:
- Gastroenterology
- Physiology
- Epithelial Transport
Background:
- Rabbit proximal colon (PC) transport differs from distal colon.
- PC lacks amiloride-inhibitable sodium absorption and does not respond to amphotericin or "stimulatory" anions.
Purpose of the Study:
- To investigate the distinct transport characteristics of rabbit proximal colon (PC).
- To elucidate the mechanism of epinephrine-stimulated ion absorption in PC.
- To examine the response of PC to various secretory stimuli.
Main Methods:
- In vitro electrical measurements and radioisotopic flux studies under short-circuit conditions.
- Assessment of ion transport rates (Na+, Cl-) under basal and stimulated conditions.
- Investigation of the effects of epinephrine (Epi), amiloride, cAMP-mediated agents, and Ca-mediated agents on ion transport.
Main Results:
- Rabbit PC is a moderately leaky epithelium with basal Na+ and Cl- transport rates near zero.
- Epinephrine (Epi) stimulates electrically silent, Na-Cl coupled absorption.
- Amiloride partially inhibits Epi-enhanced Na+ absorption.
- cAMP-mediated and Ca-mediated secretagogues exhibit antiabsorptive effects on Na+ and Cl- transport after Epi stimulation.
Conclusions:
- Rabbit PC displays unique transport properties, differing significantly from the distal colon.
- An epinephrine-sensitive, sodium-chloride coupled absorptive pathway exists in the PC.
- PC responds to secretory stimuli with antiabsorption, not electrogenic secretion.