Cardiac and red blood cell glutathione peroxidase: results of a prospective randomized trial in patients on total parenteral nutrition.

Oxygen derived free radicals and peroxides result from many antitumor treatments, including radiation and anthracyclines. Doxorubicin cardiotoxicity is thought to result from free radical induced lipid peroxidation. The heart has less active detoxification enzymes than does the liver and depends on selenium dependent glutathione peroxidase (GSH-PX) for this function. We did a sequential prospective trial in patients with totally controlled parenteral diets to examine the activity of red blood cell GSH-PX in patients with and without malignant disease. Decreased GSH-PX activity was found in 54% of the patients on parenteral nutrition and was more common in the older of these patients and in those with the greatest weight loss. In the absence of selenium supplementation, the RBC GSH-PX activity declines steadily, but with supplementation this was prevented or reversed. Because selenium deficiency can manifest as a cardiomyopathy, we measured the enzyme activity in the hearts of five patients who had died. The cardiac enzyme activity correlated strongly with the RBC levels. Significantly decreased GSH-PX has been shown in animals to be associated with changes in other enzymes critical both to activation and detoxification of carcinogens as well as antitumor drugs. Abnormality of selenium status might be a previously unsuspected contributor to interpatient variation in drug effects.