valinomycin and Leukemia--Myeloid

The membrane potential responsiveness of human myeloid leukemia cells (ML-1 line) was studied with the voltage sensitive fluorescent dye diS-C3-(5). The experimental procedure used in this study enabled us to assess the magnitude of the membrane potential change in cells treated with ouabain, 12-0-tetradecanoylphorbol-13-acetate (TPA) and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP), relative to the membrane potential in the untreated control. Inhibition of the Na, K-ATPase by ouabain was followed by a (20 +/- 4) mV depolarization. In undifferentiated homogeneous cell population TPA caused a (19.4 +/- 4.4) mV depolarization while FMLP had virtually no effect. Cells in which granulocytic or monocytic differentiation was induced by retinoic acid or 1,25-dihydroxyvitamin D3 exhibited under the effect of TPA a (57.8 +/- 7.1) mV and (34.8 +/- 10.9) mV depolarization, respectively. A very small transient depolarization was also observed up on treating of the cells with FMLP. The changes in the membrane potential responsiveness in the induced cells are obviously connected with the cell differentiation.

Topics: Benzothiazoles; Carbocyanines; Cell Differentiation; Fluorescence; Granulocytes; Humans; Kinetics; Leukemia, Myeloid; Membrane Potentials; Monocytes; N-Formylmethionine Leucyl-Phenylalanine; Ouabain; Sodium-Potassium-Exchanging ATPase; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Valinomycin

The fluorescence of the voltage sensitive dye, diS-C3-(5), has been analyzed by means of synchronous excitation spectroscopy. Using this rather rare fluorescence technique we have been able to distinguish between the slightly shifted spectra of diS-C3-(5) fluorescence from cells and from the supernatant. It has been found that diS-C3-(5) fluorescence in the supernatant can be selectively monitored at lambda exc = 630 nm and lambda em = 650 nm, while the cell associated fluorescence can be observed at lambda exc = 690 nm and lambda em = 710 nm. A modified theory for the diS-C3-(5) fluorescence response to the membrane potential is presented, according to which a linear relationship exists between the logarithmic increment of the dye fluorescence intensity in the supernatant, 1n I/I degrees, and the underlying change in the plasma membrane potential, delta psi p = psi p - psi p degrees. The theory has been tested on human myeloid leukemia cells (line ML-1) in which membrane potential changes were induced by valinomycin clamping in various K+ gradients. It has been demonstrated that the membrane potential change, delta psi p, can be measured on an absolute scale.

Topics: Benzothiazoles; Carbocyanines; Fluorescent Dyes; Humans; Kinetics; Leukemia, Myeloid; Mathematics; Membrane Potentials; Potassium; Spectrometry, Fluorescence; Tumor Cells, Cultured; Valinomycin