Induction of HSPs and antioxidant defense enzymes during activation of free radical oxidation at the early stage of hypokinesia.

We studied the stress component of the early stage of hypokinesia during hindlimb unloading. The intensity of free radical processes was evaluated and the content of protective proteins (antioxidant defense enzymes and proteins of the HSP family) was measured in the heart and liver. Three-hour hypokinesia increased the content of constitutive protective proteins, including hemoxygenase-2 and antioxidant defense enzymes, in the heart. Hypokinesia for 72 h was accompanied by more potent activation of antioxidant defense enzymes and increase in the content of inducible hemoxygenase-1, which leads to partial compensation of activated free radical oxidation. In the liver, hypokinesia of different duration suppressed the protective systems: the synthesis of inducible and constitutive hemoxygenases and antioxidant defense enzymes decreased, while the sensitivity of liver membrane structures to reactive oxygen species increased. We revealed a tissue-specific response to hypokinesia: pronounced damaging effect predominated in the liver and partial compensation of elevated production of reactive oxygen species was observed in the heart due to activation of protective systems.