[The effect of apoptosis inductor dexamethasone on the energy exchange and ultrastructure of plant cells].

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 ofmitochondrial electron transport chains. This suggestion is supported by the fact that succinate prevented DM-induced inhibition of respiration. Furthermore, stabilization of intracellular pH 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.