Endothelin(B) receptor activates NHE-3 by a Ca2+-dependent pathway in OKP cells.
To examine the mechanisms by which endothelin (ET) regulates the Na/H antiporter isoform, NHE-3, OKP cells were stably transfected with ET(A) and ET(B) receptor cDNA. In cells overexpressing ET(B), but not ET(A) receptors, ET-1 increased Na/H antiporter activity (JNa/H). This effect was inhibited by a nonselective endothelin receptor blocker and by a selective ET(B) receptor blocker but was not inhibited by an ET(A) selective receptor blocker. In ET(B)-overexpressing cells, 10(-8) M ET-1 inhibited adenylyl cyclase, but protein kinase A inhibition and pertussis toxin pretreatment did not affect Na/H antiporter activation by ET-1. ET-1 caused a transient increase in cell [Ca2+], followed by a sustained increase. Increases in cell [Ca2+] were partially inhibited by pertussis toxin. ET-1-induced increases in J(Na/H) were 50% inhibited by clamping cell [Ca2+] low with BAPTA, and by KN62, a Ca-calmodulin kinase inhibitor. Inhibitors of protein kinase C, cyclooxygenase, lipoxygenase, and cytochrome P450 and cyclic GMP were without effect. In ET(A)-overexpressing cells, ET-1 increased cell [Ca2+] but did not increase JNa/H. In summary, binding of ET-1 to ET(B) receptors increases Na/H antiporter activity in OKP cells, an effect mediated in part by increases in cell [Ca2+] and Ca-calmodulin kinase. Increases in cell [Ca2+] are not sufficient for Na/H antiporter activation.
Chu
T S
TS
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, 75235-8856, USA.
Peng
Y
Y
Cano
A
A
Yanagisawa
M
M
Alpern
R J
RJ
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D016232:Endothelins / Q000378:metabolism; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D014162:Transfection
D016232:Endothelins; D017466:Receptors, Endothelin; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D002118:Calcium