Pharmacological characterization of stably transfected Na+/H+ antiporter isoforms using amiloride analogs and a new inhibitor exhibiting anti-ischemic properties.
A fibroblast mutant cell line devoid of Na+/H+ exchange was used to stably express cDNAs encoding the NHE1, NHE2, and NHE3 Na+/H+ antiporters. Pharmacological studies using amiloride and two of its 5-N-substituted derivatives, 5-N-dimethyl amiloride and 5-N-(methyl-propyl)amiloride (MPA), demonstrate that the NHE1 isoform is the ubiquitously expressed amiloride-sensitive Na+/H+ antiporter (Ki of 0.08 microM for MPA), whereas the NHE2 and NHE3 isoforms exhibit a lower affinity for these inhibitors (Ki of 0.5 microM and 10 microM, respectively, for MPA) and are therefore likely to be members of the epithelial Na+/H+ exchanger's family. In addition, we have used this system to test a new Na+/H+ exchanger inhibitor possessing anti-ischemic properties on myocardial cells [(3-methylsulphonyl-4-piperidinobenzoyl) guanidine methanesulphonate]. This compound inhibits competitively NHE1 (Ki of 0.16 microM) with a much greater affinity than NHE2 and NHE3 (Ki of 5 microM and 650 microM, respectively) and therefore appears to be much more discriminative between these two classes of antiporter isoforms than the amiloride-related molecules. These results suggest an explanation for the observed difference of physiological effects between amiloride and HOE694, and identify this new inhibitor as a useful tool for studies of Na+/H+ exchange.
Counillon
L
L
Centre de Biochimie, Université de Nice-Sophia Antipolis.
Scholz
W
W
Lang
H J
HJ
Pouysségur
J
J
D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D018076:DNA, Complementary; D006146:Guanidines / Q000494:pharmacology*; D017202:Myocardial Ischemia / Q000188:drug therapy*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D013450:Sulfones / Q000494:pharmacology*; D014162:Transfection
D018076:DNA, Complementary; D006146:Guanidines; D011994:Recombinant Proteins; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C084633:5-(N-methyl-N-propyl)amiloride; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; C039465:5-dimethylamiloride; D000584:Amiloride