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

2. INTRODUCTION

Vitamin C, or L-ascorbic acid, is synthesized in the liver of most mammals from glucose (1). However, humans, higher primates, and guinea pigs lack the ability to synthesize the vitamin, and so must rely on efficient mechanisms for its absorption, transport, and maintenance within tissues (2). Newly absorbed ascorbate is distributed to tissues in the blood plasma, in which it is one of the most important antioxidants. Not only does ascorbate directly consume oxidant free radicals in plasma, but it also protects and recycles vitamin E or alpha-tocopherol in lipoproteins and probably in erythrocytes. The two-electron oxidized form of ascorbate, dehydroascorbic acid (DHA) is in turn rapidly taken up by erythrocytes and recycled to ascorbate. The uptake, recycling, and function of ascorbate in the erythrocyte is the subject of this review.