[Interrelationship between structural and functional modifications in the membranes of the sarcoplasmic reticulum following lipid peroxidation].

Structural and functional modifications of sarcoplasmic reticulum membranes from skeletal muscles by molecular oxygen was studied. Lipid peroxidation (accumulation of 5-10 nmoles hydroperoxides/mg lipids) results in membrane permeability increase for Ca2+-ions whereas the activity of Ca2+-dependant ATPase preserved unchanged. In the temperature range 5-30 degrees C decrease of solubilization parameter alpha (for nitroxide radical 2,2,6,6-tetramethylpiperidin-1-oxyl) was registered while alpha reached the control values at temperatures higher than 30 degrees C. Further increase in lipoperoxide content (more than 20 nmoles/mg lipids) lead to inhibition of Ca2+dependant ATPase. In this case alpha was lower than in intack membranes in the whole temperature interval investigated. The loss of Ca2+-accumulating capacity is explained on the basis of peroxide clusters formation in lipid bilayer regions of sarcoplasmic membrane. One of the mechanisms of Ca2+-dependant ATPase inhibition after lipid peroxidation is the deficiency of polyunsaturated fatty acyls in microenvironment of the enzyme.