Colonic sodium-potassium adenosine triphosphate subunit gene expression: ontogeny and regulation by adrenocortical steroids.
Mineralocorticoids and glucocorticoids exhibit overlapping but distinct effects on transepithelial sodium transport in the descending colon. Na,K-ATPase, the major sodium pump, has been variously reported to be regulated by one or both classes of steroids. The present studies explore the ontogeny and steroidal regulation of Na,K-ATPase alpha- and beta-subunit mRNA levels in the descending colon. In descending colon, subunit mRNA levels are low before birth, increasing to reach adult levels at approximately day 25. Dexamethasone treatment caused a rapid dose-dependent increase in colonic Na,K-ATPase subunit mRNA levels. The specific glucocorticoid RU26988 also increased subunit mRNA levels. Aldosterone administration, at doses adequate to yield a profound antinatriuresis, did not alter subunit mRNA levels. Carbenoloxone sodium produced an approximately 3-fold increase in subunit mRNA levels in intact but not adrenalectomized rats. We have demonstrated that Na,K-ATPase subunit gene expression is: 1) low in the fetal colon but achieves plateau levels by day 25; 2) acutely regulated by corticosteroids via type II rather than type I receptors; and 3) increased by carbenoxolone sodium, presumably as a result of increased occupancy of the type II receptor by corticosterone.
Fuller
P J
PJ
Medical Research Centre, Prince Henry's Hospital, Melbourne, Australia.
Verity
K
K
D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D000450:Aldosterone / Q000494:pharmacology; D000732:Androstanols / Q000494:pharmacology; D000818:Animals; D002229:Carbenoxolone / Q000494:pharmacology; D003106:Colon / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development; D003513:Cycloheximide / Q000494:pharmacology; D015342:DNA Probes; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D008297:Male; D009693:Nucleic Acid Hybridization; D015347:RNA Probes; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics*; D014404:Tubulin / Q000235:genetics
D000305:Adrenal Cortex Hormones; D000732:Androstanols; D015342:DNA Probes; D015347:RNA Probes; D012333:RNA, Messenger; D014404:Tubulin; D000450:Aldosterone; C038341:RU 26988; D003907:Dexamethasone; D003513:Cycloheximide; D000254:Sodium-Potassium-Exchanging ATPase; D002229:Carbenoxolone