Changes in 45Ca and 109Cd uptake, membrane potential and cell pH in Saccharomyces cerevisiae provoked by Cd2+.
The effect of Cd2+ poisoning of Saccharomyces cerevisiae on 45Ca, 109Cd and [14C]tetraphenylphosphonium (TPP) uptake and cell pH was examined. At Cd2+ concentrations that produced substantial K+ efflux the rates of uptake of 45Ca, 109Cd and [14C]TPP increased progressively during incubation of the cells with Cd2+, and the cell pH was lowered concomitantly. The initial rates of uptake of the divalent cations and of TPP were increased in cells pre-loaded with Cd2+, which shows that stimulation of the ion fluxes was exerted by the Cd2+ that accumulated in the cells. The distribution ratio of TPP between cells and medium, however, was decreased by Cd2+. Although hyperpolarization of the cell membrane by Cd2+ cannot be excluded, it is argued that Cd2+ primarily stimulated divalent cation uptake by increasing the cation permeability of the cell membrane allowing the cations to enter the cells more easily.
Kessels
B G
BG
Laboratory of Chemical Cytology, RC University, Toernooiveld, The Netherlands.
Theuvenet
A P
AP
Peters
P H
PH
Dobbelmann
J
J
Borst-Pauwels
G W
GW
D002104:Cadmium / Q000378:metabolism*; D002105:Cadmium Poisoning; D002118:Calcium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects*; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000378:metabolism
D002104:Cadmium; D002118:Calcium