Antioxidant status and indexes of oxidative stress during consecutive days of exercise

We tested whether consecutive days of prolonged submaximal exercise would result in oxidant stress sufficient to alter blood antioxidant profiles, progressively change and exhaust blood and plasma antioxidants, and damage RNA. Eleven moderately trained males (24.3 +/- 1.1 yr) exercised 90 min at 65% peak O2 uptake on a cycle ergometer for 3 consecutive days. During day 1 exercise, blood reduced glutathione (GSH) declined 55 +/- 10% and oxidized glutathione (GSSG) increased 28 +/- 7% within 15 min. Total blood glutathione did not significantly change during exercise. GSH levels returned to baseline after 15 min of recovery. On day 3, preexercise GSH and GSSG levels were not significantly different from day 1 preexercise values; essentially similar results were obtained during exercise and recovery. During day 1 exercise, plasma total ascorbate (ascorbate + dehydroascorbate) increased from 53.8 +/- 9.3 to 59.0 +/- 11.3 microM, and percent reduced ascorbate increased from 77.6 +/- 9.3 to 87.3 +/- 9.7%. During day 3 exercise, plasma ascorbate changes were similar to those on day 1. Plasma vitamin E did not change due to exercise on either day 1 or 3. RNA adducts, urinary 8-hydroxyguanosine, did not change significantly due to exercise. Observed increases in GSH oxidation indicate the presence of oxidant stress during prolonged submaximal exercise. Similar redox changes on consecutive days of exercise, with recovery to preexercise values within 15 min, indicate no evidence of persistent or cumulative exercise effects on blood glutathione redox status.(ABSTRACT TRUNCATED AT 250 WORDS)