^<23>Na- and ^1H-NMR Studies of the Action of Chlorpromazine and Imipramine on Nigericin-Mediated Na^+ Transport across Phosphatidylcholine Vesicular Membranes

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In order to elucidate the action of chlorpromazine (CPZ) and imipramine (IMP) on nigericin-mediated Na^+ transport across phosphatidylcholine vesicular membranes, ^<23>Na nuclear magnetic resonance was applied to the exchange system of Na^+ ions present at the same concentration inside and outside unilamellar vesicles. CPZ and IMP added to the vesicles in micromolar concentrations produced an equal increase in the carrier-transport rate. The kinetic analysis, together with ^1H-NMR observations of the reduction in membrane fluidity produced by the drugs and on the direct interaction between drugs and nigericin, allowed us to conclude that the drug-induced promotion of transport occurred not from the formation step of the Na^+-nigericin complex nor from its diffusion step, but from its dissociation step. The formation of an adduct between drug and nigericin could be the cause of the drug effect and this proceeded much more efficiently at a membrane-water interface (stability constant K_b; 3×10^5M^<-1>) than in methanol (K_b; 5×10^2M^<-1>). The reason for the difference is also discussed.
公益社団法人日本薬学会の論文
1994-03-15