EFFECT OF SUPPLEMENTATION WITH ANTIOXIDANTS (ALPHA-TOCOPHEROL AND ASCORBIC-ACID) ON MARKERS OF RENAL TUBULAR INJURY IN CARDIAC-SURGERY PATIENTS

Cardiac surgery is accompanied by the risk of ischaemia-reperfusion in jury to both myocardial and peripheral tissues like the kidney due to the generation of oxygen-derived free radicals. Supplementation with c hain-breaking antioxidants may trap free radicals and help protect tis sues from injury. We therefore examined the effect of pre-treating car diac surgery patients with alpha-tocopherol (vitamin E) and ascorbic a cid (vitamin C) or placebo on a hypoxia-sensitive tissue, the renal pr oximal tubule. Sixty-nine subjects undergoing elective coronary artery bypass grafting participated in a prospective, double-blind, placebo controlled randomized trail, receiving either placebo or both 750 IU/d L-alpha-tocopherol per day for 7-10 days, and 1 g ascorbic acid 12h pr ior to surgery. Plasma alpha-tocopherol concentrations fell from eleva ted to normal levels in the supplemented group and from normal to negl igible levels in the placebo group. Renal tubular markers (N-acetyl-be ta-D-glucosaminidase, adenosine deaminase binding protein, and gamma-g lutamyl transpeptidase) increased significantly relative to creatinine in both groups following surgery (P<0.001). However, there were no di fferences between the two patient groups. Thus, although antioxidant s upplementation prior to cardiac surgery prevented the depletion of the primary lipid-soluble antioxidant in plasma (alpha-tocopherol), renal tubular injury was not measurably reduced.