Interaction of ethidium bromide with yeast cells investigated by electron probe X-ray microanalysis

Abstract

Summary. K + efflux provoked by ethidium proceeds partiallyas an all-or-none effect by which the diffusion barrier for K + is disrupted and partially from still intact cells, presumably by exchange against ethidium. This is shown by the application of an electron probe microanalysis X-ray technique by which the K + content of a number of individual cells is analyzed.

All-or-none K+ efflux from yeast cells induced by calmodulin antagonists

“…Similar results have been found previously for the effect of several inhibitors of the yeast plasma membrane ATPase [4,5]. The inhomogeneity of the cell size population increases transiently during compound 48/80-induced K+ loss and concomitant cell shrinkage.…”

The concentration dependence of the depolarization of yeast by monovalent cations

“…The times at which DMP or the salts were added are indicated in the figures, in the experiments referring to Figs. 4-6 the total added ionic strength was kept constant at 30 mM by means of choline chloride in order to rule out indirect effects of the ionic strength upon DMP uptake into the cells due to changes in the surface potential [9]. As a measure for DMP uptakewe determined the fluorescence of the suspensionE by means of an Aminco SPF 500 spectrofluorim~ter at excitation and emission wavelengths of 470 and 565 rim, respectively.…”

Interactions of fungi with toxic metals

“…Such observations also mean that measured net K"ê fflux from yeast cells exposed to xenobiotics is less than K^ efflux from the affected cells where an all-ornone process occurs (Borst-Pauwels, 1988). Assays where K^ release is used as an index of toxicity should therefore be cautiously interpreted and preferably in conjunction with alternative estimations of viability (Mowll & Gadd, 1983;BorstPauwels et al, 1983;Theuvenet et al, 1987;BorstPauwels, 1988). In addition, where a potentiallytoxic divalent cation induces K^ efflux by increasing membrane permeability, the uptake of other cations may be increased.…”

“…K^ efflux induced by Mn'•^^ Co'^ Ni^^, Cu'^ Zn^^ and Cd'+ showed two phases, reversible at low concentrations (^ 5 JUM) and irreversible at high concentrations (5-100/iM depending on the metal examined) which also caused complete inhibition of K"^ uptake (White & Gadd, 1987 a, fe). K^ loss from 5. cerevisiae in response to toxic agents may be an all-or-none effect for individual cells (Kuypers & Roomans, 1979;Borst-Pauwels, Theuvenet & Stols, 1983 ;Theuvenet etal., 1983Theuvenet etal., , 1987Belde et al, 1988;Borst-Pauwels, 1988). When a population of this yeast consisting of Cd^^-sensitive and Cd^^-resistant cells were exposed to Cd'-^, the Cd^^-resistant cells subsequently absorbed the K^ lost by the sensitive cells (Belde et al, 1988).…”