Regulation of Na,K-ATPase expression by endothelin-1 in transformed human ciliary non-pigmented epithelial (HNPE) cells.
Endothelin-1 (ET-1) (1-100 nM) decreases the activity of Na,K-ATPase, a key enzyme responsible for aqueous humor formation, in transformed human non-pigmented ciliary epithelial (HNPE) cells. The present study sought to determine if ET-1 alters the expression of the catalytically active alpha subunit of Na,K-ATPase in HNPE cells and identify mechanisms underlying these effects. We report that acute (15 and 30 min) treatment with ET-1 results in an increase in mRNA expression of the alpha 1 subunit of Na,K-ATPase. Similar to ET-1's effects, ouabain (100 microM), a selective inhibitor of Na,K-ATPase, and monensin (10 microM), a sodium ionophore, also increased Na,K-ATPase expression in HNPE cells. The increase in Na,K-ATPase expression by short-term treatment with ouabain and monensin was dependent on their ability to elevate intracellular sodium concentrations. However, acute ET-1 treatment mediated increase in Na,K-ATPase expression was independent of changes in intracellular sodium. A prolonged (24 hr) ET-1 treatment results in an increase in both mRNA and protein levels of the alpha 1 subunit of Na,K-ATPase. These observations suggest that ET-1 could play a homeostatic role in modulating aqueous humor formation by having differential effects on the activity and expression of Na,K-ATPase by the ciliary epithelium in the eye.
Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA. krishna@hsc.unt.edu
Raghu R
RR
Krishnamoorthy
Ganesh
G
Prasanna
Rachel
R
Dauphin
Christina
C
Hulet
Neeraj
N
Agarwal
Thomas
T
Yorio
D002461:Cell Line, Transformed; D002924:Ciliary Body / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007223:Infant; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis* / Q000235:genetics
D019332:Endothelin-1; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase