The effects of 2-[4-[(2,5-difluorophenyl) methoxy]phenoxy]-5-ethoxyaniline 
(SEA0400), a newly synthesized Na(+)-Ca(2+) exchanger (NCX) inhibitor, on the 
NCX current and other membrane currents were examined in isolated guinea-pig 
ventricular myocytes and compared with those of 2-[2-[4-(4-nitrobenzyloxy) 
phenyl]ethyl]isothiourea (KB-R7943). SEA0400 concentration-dependently inhibited 
the NCX current with a 10 fold higher potency than that of KB-R7943; 1 microM 
SEA0400 and 10 microM KB-R7943 inhibited the NCX current by more than 80%. 
KB-R7943, at 10 microM, inhibited the sodium current, L-type calcium current, 
delayed rectifier potassium current and inwardly rectifying potassium current by 
more than 50%, but SEA0400 (1 microM) had no significant effect on these 
currents. These results indicate that SEA0400 is a potent and highly selective 
inhibitor of NCX, and would be a powerful tool for further studies on the role 
of NCX in the heart and the therapeutic potential of its inhibition.