Effect of ADP on Na(+)-Na(+) exchange reaction kinetics of Na,K-ATPase.

ABSTRACT: The whole-cell voltage-clamp technique was used in rat cardiac myocytes to investigate the kinetics of ADP binding to phosphorylated states of Na,K-ATPase and its effects on presteady-state Na(+)-dependent charge movements by this enzyme. Ouabain-sensitive transient currents generated by Na,K-ATPase functioning in electroneutral Na(+)-Na(+) exchange mode were measured at 23 degrees C with pipette ADP concentrations ([ADP]) of up to 4.3 mM and extracellular Na(+) concentrations ([Na](o)) between 36 and 145 mM at membrane potentials (V(M)) from -160 to +80 mV. Analysis of charge-V(M) curves showed that the midpoint potential of charge distribution was shifted toward more positive V(M) both by increasing [ADP] at constant Na(+)(o) and by increasing [Na](o) at constant ADP. The total quantity

SUBMITTER: Peluffo RD 

PROVIDER: S-EPMC1304497 | biostudies-literature | 2004 Aug

REPOSITORIES: biostudies-literature