Monensin-mediated antiport of Na+ and H+ across liposome membrane

Biochim Biophys Acta. 1991 Apr 26;1064(1):103-10. doi: 10.1016/0005-2736(91)90416-6.


The mechanism of monensin-mediated transport of Na+ and H+ across large unilamellar liposome membrane was investigated. The inside negative membrane potential (delta psi) was generated by the addition of monensin to the liposomes with an outward Na+ gradient. The effects of intravesicular H+ bufferring power and medium pH on the initial rates of delta psi formation, Na+ efflux and H+ influx were examined. The results showed that (i) the initial Na+ flux (JNa) was larger than the initial H+ flux (JH) at any H+ bufferring power, (ii) the JH increased with increasing inner buffer concentration, but the effect of H+ bufferring power on the JNa was small, (iii) the initial rate of delta psi formation increased linearly with the increase in the value of (JNa-JH), and (iv) the JNa increased with increasing H+ concentration. The generation of delta psi was not due to H+ leak from the liposome, since the delta psi was generated even when H+ concentration gradient was inwardly directed. The monensin-mediated transport of Na+ and H+ in this system occurred at the ratio of Na+/H+ greater than 1.0 and the resultant net electric charge efflux is the cause of the inside negative membrane potential. Tetraphenylphosphonium retarded both the delta psi formation and the H+ influx, but did not affect the Na+ efflux, suggesting that the driving force of H+ influx is the inside negative membrane potential generated by Na+ efflux. This idea also well accounts for the observed H+ bufferring power effects on the Na+ efflux, H+ influx and delta psi formation. It was suggested that Na+ was transported in the form of 1:1 complex between protonated monensin and Na+.

MeSH terms

  • Arylsulfonates
  • Biological Transport / drug effects
  • Buffers
  • Carrier Proteins / metabolism*
  • Hydrogen / metabolism
  • Hydrogen-Ion Concentration
  • Liposomes / metabolism*
  • Membrane Potentials
  • Monensin / pharmacology*
  • Onium Compounds / pharmacology
  • Organophosphorus Compounds / pharmacology
  • Sodium / metabolism
  • Sodium-Hydrogen Exchangers


  • Arylsulfonates
  • Buffers
  • Carrier Proteins
  • Liposomes
  • Onium Compounds
  • Organophosphorus Compounds
  • Sodium-Hydrogen Exchangers
  • Hydrogen
  • Monensin
  • Sodium
  • pyranine
  • tetraphenylphosphonium