Reactive oxygen species produced from chromate pigments and ascorbate.

The reactions of various chromate pigments and ascorbate were investigated by an ESR spin trapping technique. Production of Cr(V) was detected directly and productions of very electrophilic reactive oxygen species (ROS) was detected via the oxidation of formate. We demonstrated previously that both dissolved oxygen and Cr (V) were essential in the production of ROS in this system, and that ROS production was inhibited by catalase. We studied here the effect of solubility of different chromate pigments: sodium, calcium, strontium, basic zinc, basic lead supported on silica, and lead and barium chromates on the production of ROS in buffered medium and cell culture medium (Dublecco's Modified Eagle medium + fetal calf serum). Sodium, calcium, basic zinc, and basic lead chromates were active in the production of ROS in presence of cell culture medium, whereas lead and barium chromates were inactive.