This study deals with the effects of the agents that dissipate the individual components of the proton motive force (short-chain fatty acids, nigericin, and valinomycin) upon the methyl viologen-coupled nitrate reductase activity in intact cells. Substitution of butyrate or acetate for chloride in Tris-buffered assay media resulted in a marked inhibition at pH 7. In a Tris--chloride buffer of neutral pH, the reaction was almost fully inhibitable by nigericin. Alkalinisation increased the IC(50) value for nigericin and decreased the maximal inhibition attained. Both types of inhibitions could be reversed by the permeabilisation of cells or by the addition of nitrite, and that caused by nigericin disappeared at high extracellular concentrations of potassium. These data indicate that nitrate transport step relies heavily on the pH gradient at neutral pH. Since the affinity of cells for nitrate was strongly diminished by imposing an inside-positive potassium (or lithium) diffusion potential at alkaline external pH, a potential dependent step may be of significance in the transporter cycle under these conditions. Experiments with sodium-depleted media provided no hints for Na(+) as a possible H(+) substitute.

• MeSH
• biologický transport účinky léků   MeSH
• draslík metabolismus   MeSH
• dusičnany metabolismus   MeSH
• ionofory farmakologie   MeSH
• koncentrace vodíkových iontů MeSH
• nigericin farmakologie   MeSH
• nitrátreduktasa MeSH
• nitrátreduktasy antagonisté a inhibitory   MeSH
• Paracoccus denitrificans účinky léků   metabolismus   MeSH
• paraquat chemie   MeSH
• protonmotorická síla účinky léků   fyziologie   MeSH
• sodík metabolismus   MeSH
• valinomycin farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• draslík MeSH
• dusičnany MeSH
• ionofory MeSH
• nigericin MeSH
• nitrátreduktasa MeSH
• nitrátreduktasy MeSH
• paraquat MeSH
• sodík MeSH
• valinomycin MeSH