[Detection by thermal denaturation of damages to the Na pump in the myocardial sarcolemma in stress and the role of lipid peroxidation in this process].

The determination of ATP-hydrolytic activity of Na pump does not always reveal the enzyme damage in vivo. The method assessing Na, K-ATPase molecular conformational stability in the rat heart sarcolemma based on thermal denaturation is suggested. After a prolonged emotional-painful stress (EPS) the activity of Na, K-ATPase dropped by 20%, as the rate of its thermal denaturation in the range of 50-60 degrees C increased 2-3-fold. Thermodynamic calculations have demonstrated a decrease in Ea, delta H and delta S* of Na, K-ATPase thermal denaturation process after EPS. An analogous enzyme damage was found after the activation of lipid peroxidation in sarcolemma membrane suspension. These results imply that essential changes in intra- and supra-molecular properties of Na, K-ATPase under EPS may be detected by thermal denaturation. Lipid peroxidation is a most likely reason for EPS-induced Na pump damage.