EFFECT OF PLASMA MEMBRANE ION PERMEABILITY MODULATORS ON RESPIRATION AND HEAT PRODUCTION OF WHEAT ROOTS
V. Ya. Alekseeva,1 L. K. Gordon, N. L. Loseva, G. G. Rachimova, A. N. Tsentsevitsky
Kazan' Institute of Biochemistry and Biophysics RAS;
1 e-mail: alekseeva@mail.knc.ru
A study was made of changes in the rates of respiration, heat production, and membrane characteristics in cells of
excised roots of wheat seedlings under the modulation of plasma membrane ion permeability by two membrane active
compounds: valinomycin (20 μM (V50)) and chlorpromazine (50 μM (CP50) and 100 μM (CP100)). Both
compounds increased the loss of potassium ions, which correlated with the lowering of membrane potential, rate of
respiration, and heat production after a 2 h exposure. The differences in alteration of these parameters were due to
specific action of either compound on the membrane and to the extent of ion homeostasis disturbance. V20 had a weak
effect on the studied parameters. V50 caused an increase of the rate of respiration and heat production, which
enhanced following a prolonged action (5 h) and were associated with ion homeostatis restoration. The extent of
alteration of membrane characteristics (an increase of potassium loss by roots, and lowering of cell membrane
potential) as well as energy expense under the action of CP50 during the first period were more pronounced than in
the presence of V50. During a prolonged action of CP50, the increase of respiration intensity and heat production
correlated with partial recovery of ion homeostatis in cells. Essential lowering of membrane potential and
substantial loss of potassium by cells, starting from the early stages of their response reaction, were followed by
inhibition of respiration rate and heat production. Alterations of the structure and functional characteristics of
excised root cells indicate the intensification of the membrane-tropic effect of a prolonged action of CP100, and the
lack of cell energy resources.
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