Open AccessUptake of Thallous Ions by Mitochondria is Stimulated by Nonactin but not by Respiration Alone
Author(s) -
SKULSKII Igor A.,
SARIS N.E Leo,
SAVINA Margarita V.,
GLASUNOV Vadim V.
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb05698.x
Subject(s) - valinomycin , ionophore , respiration , chemistry , membrane potential , mitochondrion , nigericin , biophysics , swelling , biochemistry , membrane , biology , anatomy , chemical engineering , engineering
Nonrepiring rat‐liver mitochondria swell in media containing high concentrations of thallous nitrate, indicating passive penetration of Tl + . This swelling could be further stimulated by 10 nM or more nonactin while even 1 μM valinomycin was without effect. Nonactin was also much more potent than valinomycin in stimulating swelling of respiring mitochondria in the presence of thallous acetate. It is evident that nonactin acts as a potent ionophore of Tl + able to promote both the passive and energized uptake of Tl + in mitochondria. The distribution of Tl + , present in trace concentrations below 1 mM, was measured during energisation by respiration both in the presence and absence of ionophores. Respiration induced net uptake of Tl + only in the presence of ionophores, though Tl + as a permeant cation was expected to sense respiration‐induced changes in the membrane potential. The data may be interpreted as indicating that no tranmembrane potential is formed upon eneergisation, but localized fields, which are able to interact with the lipophilic inophore complexes of Tl + , but not with the hydrophilic cation Tl + . This interpretation is valid only if thermodynamic equilibrium has been reached.