THE EFFECT OF APOPTOSIS INDUCTOR DEXAMETHASONE ON THE ENERGY EXCHANGE AND ULTRASTRUCTURE OF PLANT CELLS
D. F. Rahmatullina,1 L. Kh. Gordon, A. A. Ponomareva, T. I. Ogorodnikova
Institute of Biochemistry and Biophysics, Kazan Science Center RAS;
1 e-mail: rahmatullina@mail.knc.ru
Changes in respiration and cell ultrastructure induced by long-term incubation with dexamethasone (DM) in excised roots of 5-day old wheat
(Triticum aestivum L.) seedlings were investigated. During 5 h incubation of roots with DM, oxygen consumption was inhibited by 20-30 %, while
respiratory coefficient did not change and its value was about 1. DM prevented from glucose-induced activation of respiration, which indicated blockade of
glycolysis and decrease in oxygen uptake by this apoptotic inductor. It has been suggested that the respiratory inhibition by DM might be also connected
with the influence of DM on the 1st segment of mitochondrial electron transport chains. This suggestion is supported by the fact that succinate prevented
DM-induced inhibition of respiration. Furthermore, stabilization of intracellular šĶ by dipeptide carnosine abolished inhibitory effect of DM on respiration.
Probably depression of oxygen consumption by DM is also due to acidification of cytoplasm. Strong vacuolization of cytoplasm, one of the characteristics
of cell death, occurred in 5 h after treatment of roots with DM. Vacuolization was to a great extent prevented by carnosine. The ultrastructure of root cells after
long-term (23 h) treatment with DM was disturbed, and oxygen consumption was also dramatically decreased. These effects of DM were in part prevented
by carnosine. The data obtained suggest that DM causes acidification of cytoplasm, disturbance of energy exchange and cytoplasm vacuolization in root cells,
and induces death of these cells.
Key words: dexamethasone, wheat roots, oxygen consumption, šĶ, glycolysis, apoptosis
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