ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
The plasmamembrane potential (ΔΨp) of murine erythroleukemia (MEL) cells has been determined by measuring the distribution of the lipophilic cation tetraphenylphosphonium (TPP+) across the plasmamembrane. TPP+ accumulation within the cells (experimental accumulation ratio, ARexp) was measured by adding 2 μM TPP+ directly to the culture flasks, avoiding any other perturbation of the experimental system. The mitochondrial contribution to ARexp, evaluated by adding carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) or 2,4-dinitrophenol (DNP), was apparently negligible in standard cultures, ARexp being substantially the same in either the absence or presence of these uncouplers. However, the addition of oligomycin produced a strong ARexp enhancement, which was abolished by FCCP, suggesting that MEL cell mitochondria are in state 3. The aspecific TPP+ binding was estimated by a new mathematical approach worked out to fit ARexp values measured in the presence of valinomycin at various extracellular K+ concentrations and plotted against the ratio of intracellular to extracellular K+ concentration ([K+]i/[K+]e). This binding was found to be close to zero in MEL cells. By applying the Nernst equation directly to ARexp values, ΔΨp of these cells was then measured; this potential varying from -65 mV to -16 mV (inside negative) is inversely related to the cell density on the culture surface on which the cells sediment (cells/cm2; CD). The dependence of ΔΨp on CD is practically eliminated by valinomycin and appears to be related to a cell interaction with the culture surface of the flasks, suggesting that in the immediate environment of MEL cells one or more factors are produced that modulate the K+ plasma membrane permeability (Pk).
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1041270104
