Interference of n-(1-[4-(4-fluorophenoxy) butyl]-piperidinyl)-n-methyl-2-benzothiazolamine with na+/h+ exchange and na+/ca2+ exchange in purified cardiac sarcolemmal membranes

The effect of R 56865 (N-[1-[4-(4-fluorophenoxy)butyl]-piperidinyl]-N-methyl-2-benzothiazolamine, CAS 104606-13-5) on Na+/H+ exchange and Na+/Ca2+ exchange was studied in isolated cardiac sarcolemmal vesicles. R 56865 inhibited Na+/H+ exchange with an ED50 of 180 mumol/l at a concentration of 0.05 mmol/l Na+. The potency of R 56865 decreased with increasing concentrations of Na+. Na+/Ca2+ exchange was also inhibited The ED50 amounted to 45 mumol/l. This ED50 was close to that of the reference compound dichlorobenzamil (ED50 = 27 mumol/l). The inhibitory potency of R 56865 on Na+/H+ and Na+/Ca2+ exchange is far too low to explain the already reported beneficial effects of this inhibitor of Na+ and Ca2+ overload during ouabain intoxication and ischemia and reperfusion.