期刊
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
卷 278, 期 5, 页码 G718-G724出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpgi.2000.278.5.G718
关键词
epithelial sodium channel; segmental heterogeneity; mineralocorticoid receptor; glucocorticoid receptor; heterodimer
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 Ih 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.
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