Study on calcium homeostasis during thymocyte apoptosis II.
Accumulation of calcium in mitochondria and endoplasmic reticulum
The activity of energy-dependent Са2+-accumulation systems in rat thymocytes mitochondria and endoplasmic reticulum (ER) in control and at the early stage of X-irradiation or H2O2-induced apoptosis were determined in experiments using the model of digitonin-permeabilized cells with addition of thapsigargin and ruthenium red. The mitochondrial Са2+-transporting system proved to be more sensitive to both apoptotic stimuli. The stationary level of Са2+, accumulated in mitochondria and initial rate of Са2+ accumulation in ER were reduced 15 min after H2O2 treatment. The parameters of mitochondrial Са2+-accumulation system in irradiated cells were decreased 30 min after irradiation. Cyclosporin A almost completely inhibited DNA fragmentation in irradiated and partly – in peroxide-treated cells. The mitochondrial calcium homeostasis imbalance is suggested to be an early event in thymocytes apoptosis initiation.
Published at the site: 2005-03-03
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