The plasma membrane electrical gradient (membrane potential) in Leishmania donovani promastigotes and amastigotes.
The equilibrium distribution of tetraphenylphosphonium bromide was used to measure the membrane potential in Leishmania donovani amastigotes and promastigotes and to investigate mechanisms underlying the maintenance of membrane potential. At pH 7.0, membrane potential ranges between -90 and -113 mV. Increasing the external concentrations of hydrogen or potassium ions decreased membrane potential as did treatments with carbonylcyanide chlorophenylhydrazone or valinomycin. These observations are consistent with a membrane potential set by hydrogen and potassium ion diffusion gradients. Anaerobiosis lowered membrane potential, suggesting the involvement of ATPase(s) in maintaining membrane potential. Membrane potential was insensitive to treatment with ouabain, demonstrating the absence of a Na+/K(+)-ATPase. Treatment with dicyclohexylcarbodiimide caused a temporary hyperpolarization of the membrane suggesting the participation of a proton ATPase in the maintenance of membrane potential. Determination of the membrane potential makes it possible to quantitate the total proton motive force which is the force for active transport across the parasite membrane.
Glaser
T A
TA
Department of Biological Sciences, University of Cincinnati, OH 45221.
Utz
G L
GL
Mukkada
A J
AJ
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D007893:Leishmania donovani / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009861:Onium Compounds / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism
D004791:Enzyme Inhibitors; D007476:Ionophores; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D000251:Adenosine Triphosphatases; C013289:tetraphenylphosphonium