title: Dexamethasone enhances expression of mitochondrial oxidative phosphorylation genes in rat distal colon.
abstract: Dexamethasone and aldosterone are major activators of Na+ reabsorption in tight epithelia. The genes whose expression mediates the steroid actions are mostly unknown. To identify such genes, we performed differential screening of a rat colon cDNA library with total 32P-labeled cDNA probes reverse transcribed from steroid-stimulated and steroid-depleted poly(A)+ RNA. Several cDNAs whose corresponding mRNA is enhanced two- to threefold after dexamethasone injection were identified. Partial sequencing indicated that four of them code for subunits of cytochrome-c oxidase and 16S mitochondrial mRNA. The dexamethasone-induced increase in mitochondrial RNA abundance could not be mimicked by a low-salt diet, found to increase plasma aldosterone from 1.0 +/- 0.1 to 12.8 +/- 1.4 nM. Induction of mitochondrial genes by adrenal steroids may serve to prevent limitation of transport by the ATP supply to the Na(+)-K+ pump under conditions of maximal stimulation of Na+ transport.
mesh_terms: D000818:Animals; D001483:Base Sequence; D003106:Colon / Q000378:metabolism*; D018076:DNA, Complementary; D003907:Dexamethasone / Q000494:pharmacology*; D003576:Electron Transport Complex IV / Q000235:genetics; D015870:Gene Expression; D015723:Gene Library; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010085:Oxidative Phosphorylation; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar
chemical_list: D018076:DNA, Complementary; D015345:Oligonucleotide Probes; D012336:RNA, Ribosomal, 16S; D003907:Dexamethasone; D003576:Electron Transport Complex IV