Early aldosterone effect in distal colon by transcriptional regulation of ENaC subunits

Aldosterone-induced sodium absorption is mediated by the epithelial Na(+) channel (ENaC). It is thought that the "early effect" is not based on genomic regulation of ENaC expression, because ENaC subunit transcription was reported to start later than Na(+) transport. We investigated electr...

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Bibliographic Details
Published in:American journal of physiology: Gastrointestinal and liver physiology 2000-05, Vol.278 (5), p.G718-G724
Main Authors: Epple, H J, Amasheh, S, Mankertz, J, Goltz, M, Schulzke, J D, Fromm, M
Format: Article
Language:English
Subjects:
Aldosterone - pharmacology
Animals
Biological Transport
Colon - physiology
Epithelial Sodium Channels
Gene Expression Regulation - drug effects
Gene Expression Regulation - physiology
In Vitro Techniques
Intestinal Mucosa - drug effects
Intestinal Mucosa - physiology
Kinetics
Male
Membrane Potentials - drug effects
Rats
Rats, Wistar
RNA, Messenger - genetics
Sodium - metabolism
Sodium Channels - genetics
Time Factors
Transcription, Genetic - drug effects
Transcription, Genetic - physiology
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Summary:Aldosterone-induced sodium absorption is mediated by the epithelial Na(+) channel (ENaC). It is thought that the "early effect" is not based on genomic regulation of ENaC expression, because ENaC subunit transcription was reported to start later than Na(+) transport. We investigated electrogenic Na(+) absorption (J(Na)) and, in identical tissues, mRNA expression of ENaC subunits in early (EDC) and late (LDC) distal colon of the rat. In both segments, 8-h in vitro incubation with 3 nM aldosterone enhanced expression of beta- and gamma-ENaC mRNA and induced J(Na). J(Na) was 10 times higher in LDC than in EDC. alpha-ENaC mRNA was unchanged in EDC, whereas it decreased in LDC. In LDC, beta- and gamma-ENaC mRNA was induced 1 h after aldosterone addition, whereas J(Na) became apparent >1 h later. Downregulation of alpha-ENaC mRNA did not take part in acute regulation because it started after a lag time of 3 h. Time correlation of beta- and gamma-ENaC induction and J(Na) stimulation suggests that the early aldosterone effect on Na(+) absorption in distal colon is caused by transcriptional upregulation of beta- and gamma-ENaC expression.
ISSN:0193-1857
1522-1547
DOI:10.1152/ajpgi.2000.278.5.g718