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 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.
Epple
H J
HJ
Department of Clinical Physiology, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, 12200 Berlin, Germany.
Amasheh
S
S
Mankertz
J
J
Goltz
M
M
Schulzke
J D
JD
Fromm
M
M
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport; D003106:Colon / Q000502:physiology*; D053503:Epithelial Sodium Channels; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000235:genetics*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
D053503:Epithelial Sodium Channels; D012333:RNA, Messenger; D015222:Sodium Channels; D000450:Aldosterone; D012964:Sodium