title: Regulation of the plasma membrane potential in Pneumocystis carinii.
abstract: Many protists use a H(+) gradient across the plasma membrane, the proton motive force, to drive nutrient uptake. This force is generated in part by the plasma membrane potential (DeltaPsi). We investigated the regulation of the DeltaPsi in Pneumocystis carinii using the potentiometric fluorescent dye bisoxonol. The steady state DeltaPsi in a buffer containing Na(+) and K(+) (standard buffer) was found to be -78+/-8 mV. In the absence of Na(+) and K(+) (NMG buffer) or Cl(-) (gluconate buffer), DeltaPsi was not significantly changed suggesting that cation and anion conductances do not play a significant role in the regulation of DeltaPsi in P. carinii. The DeltaPsi was also not affected by inhibitors of the Na(+)/K(+)-ATPase, ouabain (1 mM), and the K(+)/H(+)-ATPase, omeprazole (1 mM). In contrast, inhibitors of the plasma membrane H(+)-ATPase, dicyclohexylcarbodiimide (100 microM), N-ethylmaleimide (100 microM) and diethylstilbestrol (25 microM), significantly depolarized the DeltaPsi to -43+/-7, -56+/-5 and -40+/-12 mV, respectively. The data support that the plasma membrane H(+)-ATPase plays a significant role in the regulation of DeltaPsi in P. carinii.
authors.affiliation: Laboratory of Molecular Parasitology, Department of Pathobiology, University of Illinois at Urbana-Champaign, 2001 S. Lincoln Av., Urbana, IL 61802, USA.
authors.forename: N
authors.initials: N
authors.lastname: VanderHeyden
authors.forename: G L
authors.initials: GL
authors.lastname: McLaughlin
authors.forename: R
authors.initials: R
authors.lastname: Docampo
mesh_terms: D002462:Cell Membrane / Q000502:physiology; D008564:Membrane Potentials; D011010:Pneumocystis / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology
chemical_list: D006180:Proton-Translocating ATPases; D000254:Sodium-Potassium-Exchanging ATPase