[Calcium homeostasis during thymocyte apoptosis. I. Increase in cytosolic Ca2+ concentration at the early stage of apoptosis induced by hydrogen peroxide].

The concentration of free cytosolic Ca2+ ([Ca2+]i), 45Ca2+ entry and the level of reduced glutathione (GSH) after x-irradiation in a dose of 4.5 Gy or 0.1 mM H2O2-treatment were investigated in isolated rat thymocytes during the period preceding electrophoretically detected DNA intranucleosomal fragmentation.

[Calcium homeostasis in the thymocyte apoptosis II. Accumulation of calcium in mitochondria and endoplasmic reticulum].

The activity of energy-dependent Ca2+-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 Ca2+-transporting system proved to be more sensitive to both apoptotic stimuli. The stationary level of Ca2+, accumulated in mitochondria and initial rate of Ca2+ accumulation in ER were reduced 15 min after H2O2 treatment.

[Lipoxygenase activity and 15-hete content of rat spleen lymphocytes after exposure to ionizing radiation].

Pretreatment of rat spleen lymphocytes with 0.5 mM A23187 had no influence on the prostaglandins E2 and F2 alpha content, but was followed by the increasing of both 15-HETE and leukotriene B4 levels. Lypoxygenase activity of lymphocytes towards exogenous substrate linoleic acid was increased within 3-12 h after 1 Gy irradiation and decreased below the control level at 24 h.

[Biochemical aspects of radiation-induced apoptosis].

Radiation-induced activation of the nuclear and cytosolic regulatory pathways, involvement of transcriptional factors and calcium in apoptotic signal transducing, DNA fragmentation at the different stages of apoptosis are discussed. The data on bcl-2 action in preventing calcium signal and apoptosis in lymphoid cells are presented.

[Inhibition of lipoxygenase activity reduces radiation-induced DNA fragmentation in lymphocytes].

Lypoxygenase activity of lymphocytes towards exogenous substrate linolic acid and the level of endogenous arachidonate metabolite 15-HETE are increased within 6 h and decreased below the control level at 24 h after 1 Gy X-ray irradiation of Wistar rats. DNA fragmentation is stimulated both in vivo within 12 h and during in vitro incubation of lymphocytes, obtained 3 h following irradiation. DNA analysis by agarose gel shows that DNA fragments are multiples of the 200 base pair unit.