Inotropic actions of BDF 9148 and DPI 201-106 and their enantiomers in guinea-pig, rat and human atria.

The positive inotropic effects of the sodium channel modulators, DPI 201-106 and BDF 9148, were tested in atrial preparations from guinea-pig, rat and man. In rat, the racemate and S enantiomer of both DPI 201-106 and BDF 9148 displayed the same efficacy as did increased extracellular Ca2+, but in guinea-pig and man, the efficacy varied between 60 and 90% of the maximum Ca2+ response. In all three species, BDF 9148 was significantly more potent than DPI 201-106 by approximately one order of magnitude. The same was evident for the S enantiomers. The R enantiomers did not inhibit the effects of the S enantiomers. We have shown pronounced differences in the efficacy and potency of the enantiomers of DPI 201-206 and BDF 9148, which may be useful for future radioligand binding studies.