Submitted on November 10, 2006
Accepted on February 9, 2007
Effects of 20-HETE on Na+ transport and Na+-K+-ATPase activity in the thick ascending loop of Henle
Ming Yu1, Bernardo Lopez1, Elisabete A. Dos Santos1, John R. Falck2, and Richard J. Roman3*
1 Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
2 Biochemistry, UT Southwestern Medical Center @ Dallas, Dallas, Texas, United States
3 Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
* To whom correspondence should be addressed. E-mail: rroman{at}mcw.edu.
Previous studies have indicated that 20-hydroxyeicosatetraenoic acid (20-HETE) inhibits Na+ transport in the medullary thick ascending loop of Henle (mTALH), but the mechanisms involved remain uncertain. The present study compared the effects of 20-HETE with those of ouabain and furosemide on intracellular Na+ concentration ([Na+]i), Na+-K+-ATPase activity and 86Rb+ uptake, an index of Na+ transport, in mTALH isolated from rats. Ouabain (2 mM) increased, while furosemide (100 µM) decreased, [Na+]i in the mTALH of rats. Ouabain and furosemide inhibited 86Rb+ uptake by 91% and 30%, respectively. 20-HETE (1 µM) had a similar effect as ouabain and increased [Na+]i from 19±1 to 30±1 mM. 20-HETE reduced Na+-K+-ATPase activity by 30% and 86Rb+ uptake by 37%, but it had no effect on 86Rb+ uptake or [Na+]i in the mTALH of rats pretreated with ouabain. 20-HETE inhibited 86Rb+ uptake by 12% and increased [Na+]i by 19 mM in mTALH pretreated with furosemide. These findings indicate that 20-HETE secondarily inhibits Na+ transport in the mTALH of the rat, at least, in part by inhibiting the Na+-K+ -ATPase activity and raising [Na+]i.
