valinomycin and malachite-green

The transport of an organic cation across a 4-5 nm liposome bilayer is observed in real time using second harmonic generation. It is proposed that an electrostatic barrier between the inside and outside of the liposome develops as the cation crosses the bilayer. This would explain why the SHG signal does not approach zero at long times. To test this mechanism, the antibiotic valinomycin, which can transport alkali ions across a phospholipid bilayer, is introduced into the system. It is found that the transport time is reduced by a factor of three from 90+/-2 s to 30+/-1 s with 1.25 x 10(-8) M valinomycin concentration, and a factor of fifteen to 6.2+/-0.2 s with 1.25 x 10(-8) M valinomycin concentration. In addition, the SHG signal approaches zero, which further supports the presence of an electrostatic barrier that can be eliminated by the alkali ion transporter valinomycin.

Topics: Ion Transport; Kinetics; Lipid Bilayers; Liposomes; Rosaniline Dyes; Valinomycin

The mitochondrial effects of submicromolar concentrations of six triarylmethane dyes, with potential applications in antioncotic photodynamic therapy, were studied. All dyes promoted an inhibition of glutamate or succinate-supported respiration in uncoupled mitochondria, in a manner stimulated photodynamically. No inhibition of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) supported respiration was observed, indicating that these dyes do not affect mitochondrial complex IV. When mitochondria were energized with TMPD in the absence of an uncoupler, treatment with victoria blue R, B, or BO, promoted a dissipation of mitochondrial membrane potential and increase of respiratory rates, compatible with mitochondrial uncoupling. This effect was observed even in the dark, and was not prevented by EGTA, Mg2+ or cyclosporin A, suggesting that it is promoted by a direct effect of the dye on inner mitochondrial membrane permeability to protons. Indeed, victoria blue R, B, and BO promoted swelling of valinomycin-treated mitochondria incubated in a hyposmotic K+-acetate-based medium, confirming that these dyes act as classic protonophores such as FCCP. On the other hand, ethyl violet, crystal violet, and malachite green promoted a dissipation of mitochondrial membrane potential, accompanied by mitochondrial swelling, which was prevented by EGTA, Mg2+, and cyclosporin A, demonstrating that these drugs induce mitochondrial permeability transition. This mitochondrial permeabilization was followed by respiratory inhibition, attributable to cytochrome c release, and was caused by the oxidation of NAD(P)H promoted by these drugs.

Topics: Animals; Ascorbic Acid; Coloring Agents; Gentian Violet; Glutamic Acid; Lissamine Green Dyes; Membrane Potentials; Mitochondria, Liver; Mitochondrial Swelling; Osmosis; Oxygen Consumption; Photosensitizing Agents; Quaternary Ammonium Compounds; Rats; Rosaniline Dyes; Tetramethylphenylenediamine; Valinomycin