ISSN:
1432-1424
Keywords:
electrical potential difference (Δψ)
;
membrane potential
;
yeast electrophysiology
;
microelectrode
;
TPP+ distribution
;
Pichia humboldtii
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Electrical potential differences across the plasma membrane (Δψ) of the yeastPichia humboldtii were measured with microelectrodes (filled with 0.1m KCl) inserted into cells immobilized in microfunnels. The registered Δψ signals were reproducible and stable for several minutes. On attainment of stable reading for Δψ the specific membrane resistanceR sp was determined by applying square-current pulses to the preparation. Both Δψ andR sp were pH dependent and displayed equal but opposite deflection, Δψ reaching its maximal value of −88±9 mV (n=13) andR sp its minimal value of 10 kΩ·cm2 (maximal conductance) at pH 6.5. Uncouplers and the polyene antibiotic nystatin depolarized the cells, decreasing Δψ to −21±15 mV (n=10) with concomitant decrease ofR sp. Comparison of Δψ values from microelectrode measurements with those calculated from the steady-state distribution of tetraphenylphosphonium ions agreed within 10 mV under all physiological conditions tested, except at pH values above 7.0. During microelectrode insertion transient voltage signals (a few msec long) were detected by means of an oscilloscope. These voltage signals were superimposed on the stable Δψ recordings described above. These short voltage signals disappeared in uncoupled cells. The closely related Δψ values obtained by two independent methods (direct measurements with microelectrodes and calculation from steady-state distribution of a lipophilic cation) provide evidence that these values reffect the true membrane potential of intact cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01993985
Permalink
