Will the Real Plasma Oxidized Glutathione Level Please Stand Up?

Following an examination of questionable transsulfuration metabolite values published by Geier et al (summary table below), e-mails were sent to the editors of Neurochemical Research and the Journal of the Neurological Sciences, alerting them to the discrepancies between these data and very different values in the published literature.

The associate editor of Neurochemical Research, Henry Sershon, forwarded my e-mail to Mark Geier (anchor author), who reviewed the information and responded to Dr. Sershon that the published values for GSSG were consistent with those of James et al in a 2004 study (which was also cited by Geier et al). In fact, a review of this study reveals that the printed mean value for plasma GSSG in control children, 0.32 nmol/L ± 0.1 (range, 0.11-0.43 nmol/L), is very similar to the control value of Geier et al (0.35 nmol/L ± 0.05). But it is also very different from the control value published by James et al in their 2006 study, 0.24 µmol/L ± 0.1, or 240 nmol/L ± 100.

To that end, I e-mailed Dr. James asking for clarification of the plasma GSSG values in her articles, and she responded that the units in the 2004 article were incorrect and should have been µmol/L, not nmol/L. Consequently this correction negates Dr. Geier's rebuttal that his values for plasma GSSG are consistent with those of James et al.

Dr. James added that she rarely sees GSSG levels greater than 0.4 µmol/L [or 400 nmol/L] in control children. Others indicate that measurements of plasma glutathione, reduced and oxidized, are highly dependent on testing procedures and vary substantially with even minor hemolysis. Still others indicate that "[i]t is not possible to distinguish between oxidized and reduced glutathione in serum or plasma," owing to very low concentrations.

* Reference cited by Geier et al.