Dramatic reduction of erythrocyte glucose-6-phosphate dehydrogenase activity in athletes participating in the ultradistance foot race Spartathlon

Objective. To investigate the effect of a long-distance endurance exercise ''Spartathlon'' on erythrocyte glucose-6-phosphate dehydrogenase (G(6)PD) activity. Material and methods. The study comprised 15 male runners, median age 36.5 years. Blood samples were obtained in the 15 min before the race and again within 15 min after the end of the race. Erythrocyte glutathione (GSH and GSSG) and plasma malonyldialdehyde were measured with HPLC methods, and total antioxidant capacity (TAC), total hyperoxides and G(6)PD activity with commercial kits. Lipids, uric acid and total bilirubin were determined with a clinical chemistry analyser. Results. Total hyperoxides were found statistically reduced, whereas total bilirubin was measured elevated post-race. Interestingly, GSSG levels were found increased (167.3 +/- 12.0 versus 219.5 +/- 20.3 mu mol/L; p < 0.005) as well as GSSG/GSH ratio (16.0 +/- 1.3 versus 20.60 +/- 1.65; p < 0.05) post-race. In contrast, G(6)PD activity was found remarkably decreased (8.72 +/- 3.10 versus 3.8 +/- 2.5 U/g Hb; p < 0.0001) pre versus post the event. Conclusion. Red blood cell G(6)PD activity in athletes may be reduced post-race as a consequence of the modulation of NADP/NADPH levels and elevation of the erythrocyte GSSG, and especially GSSG/GSH ratio, resulting in an impairment of the hexose monophosphate shunt.