Differential regulation of Na+-K+-ATPase gene expression by corticosteriods in vascular smooth muscle cells.
To determine whether gluco- and mineralocorticoids have specific actions on Na+-K+-ATPase gene expression in vascular tissue, we used Northern blot analysis to compare the effects of dexamethasone (Dex) and aldosterone (Aldo) on Na+-K+-ATPase alpha1 and beta1-subunit mRNA expression in cultured vascular smooth muscle cells from rat aortae. Dex at 10(-6)M increased alpha1 -mRNA level 2.5-fold at 24 h and beta1-mRNA level 9.9-fold at 12 h. Aldo at 10(-6)M increased alpha1-mRNA 2.7-fold at 48 h and beta1-mRNA level 10.9-fold at 6 h. The half-maximal stimulation of both alpha1 and beta1-mRNA levels occurred at a concentration of 5-7 X 10(-9)M Dex, whereas it occurred at a concentration of 2-3 X 10(-9)M Aldo. The glucocorticoid receptor antagonist RU-38486 inhibited both Dex- and Aldo-mediated induction of beta1-mRNA. The mineralocorticoid receptor antagonist spironolactone inhibited Aldo-mediated induction of beta1-mRNA, whereas it had no effect on Dex-mediated induction of beta1-mRNA. Removal of Na+ from the extracellular medium (isosmotic replacement with choline) caused no effect on Dex-mediated induction beta1-mRNA, whereas it inhibited Aldo-mediated induction of beta1-mRNA. Addition of a specific inhibitor of the Na+/H+ exchange, ethylisopropylamiloride, had no effect on Dex-mediated induction of beta1-mRNA, whereas it resulted in a significant inhibition of Aldo-mediated induction of beta1-mRNA. We conclude that 1) both Dex and Aldo induce Na+-K+-ATPase alpha1- and beta1-mRNA expression in a time- and dose-dependent manner; 2) Dex-mediated induction of beta1-mRNA occurs only through glucocorticoid receptors, whereas Aldo-mediated induction of beta1-mRNA occurs through both gluco- and mineralocorticoid receptors; and 3) Dex-mediated induction of beta1-mRNA occurs through Na+-independent mechanisms, whereas Aldo-mediated induction of beta1-mRNA, at least in part, occurs through Na+-dependent mechanisms, including stimulation of the Na+/H+ exchange.
Muto
S
S
Department of Nephrology, Jichi Medical School, Minamikawachi, Japan.
Nemoto
J
J
Ohtaka
A
A
Watanabe
Y
Y
Yamaki
M
M
Kawakami
K
K
Nagano
K
K
Asano
Y
Y
D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D000450:Aldosterone / Q000494:pharmacology*; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001013:Aorta, Thoracic; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D015735:Mifepristone / Q000494:pharmacology; D000451:Mineralocorticoid Receptor Antagonists; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis*; D013148:Spironolactone / Q000494:pharmacology
D000305:Adrenal Cortex Hormones; D000451:Mineralocorticoid Receptor Antagonists; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; D013148:Spironolactone; D015735:Mifepristone; D000450:Aldosterone; D000584:Amiloride; D003907:Dexamethasone; D000254:Sodium-Potassium-Exchanging ATPase; C039614:ethylisopropylamiloride