Fig. 4.

(A) Propionic acid (PPA) infusions in rats induces a significant increase in lipid and protein oxidation, supportive of increased oxidative stress via increased oxidant production and decreased antioxidant defenses in homogenates of discrete regions of rodent brain consistent with findings in patients with autism. Interestingly, brain stem appears relatively unaffected. (B) PPA-treated rats showed significantly decreased total GSH, a decreased activity of GPx, but an increase in the activity of GST. Conversely, the activity of GR was unchanged. These findings suggest that GSH may be involved in the metabolic clearance of PPA, or alternatively, the synthesis of GSH was impaired by PPA. The observed reduction of the activity of GPx may be due to the decreased availability of GSH, a cofactor of GPx or may reflect an overall reduction in antioxidant defenses induced by PPA. Black bars indicate PPA-treated animals; white bars indicate PBS (vehicle)-treated animals. Figures modified with permission from MacFabe et al. (2008). Reproduced with permission from Science (American Association for the Advancement of Science).