ASCORBATE FUNCTION AND METABOLISM IN THE HUMAN ERYTHROCYTE

James M. May

Departments of Medicine and Molecular Physiology and Biophysics, 736 Medical Research Building II, Vanderbilt University School of Medicine, Nashville, TN 37232-6303 USA

Received 11/5/97 Accepted 11/9/97

7. PERSPECTIVE

Ascorbate in the blood plasma provides a crucial link between ascorbate uptake by the intestine and its delivery to the tissues. The vitamin also contributes to the antioxidant reserve of blood, especially in areas of oxidant stress in the vascular bed, such as those involved with inflammation or atherosclerosis. The ability of the erythrocyte to recycle ascorbate may be very important to the maintenance of this antioxidant reserve. However, ascorbate can be a two-edged sword, and function as a powerful prooxidant in the presence of transition metals such as the ferric ion (24). Given that the erythrocyte contains the largest store of iron in any cell, avoidance of hemolysis and release and degradation of hemoglobin is crucial. Sparing or recycling of alpha-tocopherol by ascorbate in the erythrocyte will tend to stabilize the erythrocyte membrane and thus prevent hemolysis. Thus the net effect is an antioxidant rather than prooxidant effect of the vitamin.