The effect of vitamin E-deficiency in isolated rat heart on the cellular defence system against free radicals during normal reperfusion after hypoxic, ischemic and Ca(2+)-free perfusion.

Abstract

We investigated whether vitamin E plays a role in the protection against potential free radical formation and related biochemical changes in hypoxic, ischemic and Ca(2+)-depleted rat heart upon normal reperfusion. In the heart of normally fed rats a decrease in the activity of superoxide dismutase and the capacity of the glutathione system, factors of the cellular protective mechanisms against free radicals, occurred upon exposure to the above mentioned treatments. This decrease was not further enhanced if vitamin E-deficient rat hearts were treated. Vitamin E-deficiency, however, led to detectable peroxidation of lipids if Ca(2+)-depleted or hypoxic hearts were reperfused. Lipid peroxidation was measured as the formation of thiobarbituric acid reactive material, which is readily formed during this process. Reflow after ischemia did not induce lipid peroxidation either in normal or in vitamin E-deficient rat heart. Since changes in Ca(2+)-homeostasis are thought to be primarily responsible for the Ca(2+)-reperfusion injury, a role for Ca(2+)-ions in lipid peroxidative processes, either directly or indirectly, seems indicated. Furthermore the results imply that even a sharp and extensive decrease of reduced glutathione, as seen upon Ca(2+)-repletion after a period of Ca(2+)-depletion, does not necessarily induce peroxidation of lipids in heart tissue. Obviously, vitamin E is very important in the protection of cardiac membranes. Replenishment of the water-soluble protective factors in the heart seems, however, more important during above mentioned treatments, especially since repair of the vitamin E-free radical is dependent on water-soluble factors.