Segmental heterogeneity of the rat colon in the response to activators of secretion on the cAMP-, the cGMP- and the Ca(2+)-pathway

The electrolyte transport was compared in proximal and distal segments of the rat colon under control conditions and after induction of secretion on the cAMP-, the cGMP- and the Ca(2+)-pathway. Baseline short-circuit current was decreased by indomethacin and tetrodotoxin in the distal colon, indicat...

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Bibliographic Details
Published in:Acta physiologica Scandinavica 1991-07, Vol.142 (3), p.375
Main Authors: Nobles, M, Diener, M, Mestres, P, Rummel, W
Format: Article
Language:English
Subjects:
8-Bromo Cyclic Adenosine Monophosphate - pharmacology
Animals
Calcium - metabolism
Carbachol - pharmacology
Chlorides - metabolism
Colforsin - pharmacology
Colon - drug effects
Colon - secretion
Cyclic AMP - metabolism
Cyclic GMP - metabolism
Epithelium - secretion
Epithelium - ultrastructure
Female
Humans
In Vitro Techniques
Prostaglandins - physiology
Rats
Rats, Inbred Strains
Sodium - metabolism
Tetrodotoxin - pharmacology
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Summary:The electrolyte transport was compared in proximal and distal segments of the rat colon under control conditions and after induction of secretion on the cAMP-, the cGMP- and the Ca(2+)-pathway. Baseline short-circuit current was decreased by indomethacin and tetrodotoxin in the distal colon, indicating a spontaneous production of neuronally acting prostaglandins. In contrast, baseline short-circuit current in the proximal colon was decreased only by indomethacin, but not by tetrodotoxin. Unidirectional flux measurements revealed that in the distal colon sodium and chloride were absorbed, while the proximal colon secreted chloride. A morphological comparison between the distal and proximal epithelium revealed that the zonulae occludentes and the microvilli were longer in the distal colon. The size of the Golgi apparatus was several times larger in the crypt than in the surface region without differences between proximal and distal colon. Distal segments were more sensitive to an activator of the Ca(2+)-pathway, carbachol, or activators of the cAMP-pathway such as forskolin and a cAMP-analogue. In contrast, the activation of the cGMP-pathway by a cGMP-analogue or by the heat-stable enterotoxin of E. coli (STa) was more effective in the proximal colon. The results give evidence for a segmental specificity with regard to the intracellular pathways responsible for the activation of secretion.
ISSN:0001-6772
DOI:10.1111/j.1748-1716.1991.tb09171.x