Ascorbate functions as an electron donor and scavenges free radicals. Dehydroascorbic acid (DHA), the oxidized form of ascorbate, is generated as a result of these reactions. While low plasma ascorbate levels have been reported in hemodialysis patients worldwide, no studies have measured DHA because it is not generalized. In this study, we aimed to clarify whether plasma ascorbate levels are low in dialysis patients and whether plasma ascorbate levels fluctuate before and after dialysis. Moreover, we applied our previously established method to measure the plasma ascorbate and DHA levels in chronic kidney disease (CKD) stage G3-G5 non-hemodialysis-dependent patients, and pre- and post-dialysis plasma ascorbate and DHA levels in CKD stage G5D hemodialysis patients. The sample size was calculated using G-power software. The pre-dialysis plasma total ascorbate levels, including DHA, were significantly (56%) lower in hemodialysis patients than in non-hemodialysis-dependent CKD patients. After dialysis, there was a 40% reduction in the plasma total ascorbate levels. Hemodialysis increased the post-dialysis plasma proportions of DHA from 37% to 55%. The study results demonstrated lower plasma total ascorbate levels in hemodialysis patients compared with in non-hemodialysis-dependent CKD patients; these low levels in hemodialysis patients were further reduced by hemodialysis and increased DHA proportion.
Keywords: ascorbate; chronic kidney disease; dehydroascorbic acid; hemodialysis; hyperkalemia; potassium; vitamin C.