[Opposite effects on antioxidant enzymes of adaptation to continuous and intermittent hypoxia].

Adaptation to continuous hypoxia under mid-mountain conditions (altitude 2100 m) decreases the content of lipid peroxidation products and the activity of superoxide dismutase and catalase in rat heart, liver, and brain, with a concomitant decline in the resistance to reperfusion arrhythmias. On the contrary, adaptation to intermittent hypoxia in the altitude chamber increases the activity of the antioxidant enzymes in the same organs, while the content of peroxidation products remains normal; at the same time, the heart becomes more resistant to reperfusion arrhythmias. The mechanism is discussed that ensures enhanced antioxidant protection in adaptation to intermittent hypoxia.

[Effects of adaptation to periodic hypoxia on Ca2+ pump of the cardiac sarcoplasmic reticulum and its resistance to endogenous damaging factors].

The adaptation of rats to periodic "altitude" hypoxia in the altitude chamber (6 hour daily at an altitude of 5000 m during a month) led to increased activity of the Ca2+ pump in the myocardial sarcoplasmic reticulum, which was associated with lower Kd values and higher calcium transport Vmax. When a cardiac homogenate was kept at 4 degrees C, autolysis resulted in a decrease in Ca2+ pump activity (which was more rapid in adapted animals than in the controls) and an equal increase in the levels of free calcium in the homogenates in the two series of experiments. The approximate data were obtained when a homogenate was incubated at 37 degrees C, but when it was incubated at 4 degrees C, the rate of Ca(2+)-pump inactivation decreased 20-fold.

[The effect of surgical stress on DNA synthesis in liver and brain cells].

Distinct alterations in the rate of DNA synthesis (an increase in the rate of reparation and a decrease in the rate of replication in nuclei and mitochondria) were detected in liver and brain cells during the stress caused by surgical operation. Within 8-10 hrs after the operation the rate of DNA reparation was increased by 40-50% in nuclei of liver cells and by 31-35% in brain cell nuclei. Replication of nuclear DNA was decreased immediately after the operation--by 33% in liver cells and by 50% in brain cells.

[Suppression of replication and activation of DNA reparative synthesis in stress and prevention of these phenomena by preliminary adaptation].

Effects of preliminary adaptation to short-term stress or to regular hypoxia on disturbances of DNA biosynthesis were studied in liver and heart tissues under conditions of emotional-painful stress (EPS). EPS was found to induced activation of DNA reparative synthesis in heart and liver tissues and affected dissimilarly DNA replication in these tissues: activation of the reaction in heart and suppression in liver tissue. Adaptation to regular hypoxia limited distinctly the burst of DNA reparative synthesis in cells of both these tissues, reduced activation of the DNA replicative synthesis in heart and prevented the stress induced depression of DNA replication in hepatic cell nuclei and mitochondria.