EFFECT OF HIGH-CONCENTRATION OF ASCORBATE ON CATALASE ACTIVITY IN CULTURED-CELLS AND TISSUES OF GUINEA-PIGS

This study showed that the inhibition of cell growth in 3T6, induced b y the supplementation of ascorbate at 0.5 mM in cultured medium, was p revented by the addition of catalase in the range of 25-750 units/mL r egardless of the degree of activity. However, cytotoxicity induced by concentrations of more than 2mM ascorbate could not be prevented even when a high level of catalase (5,000 units/mL) was added to the medium . Catalase activity in medium supplemented with ascorbate decreased wi th incubation time; the higher the concentration of ascorbate, the gre ater the decrease in catalase activity. These results indicate that ev en though catalase is present at a high concentration in the medium, i t cannot prevent cytotoxicity by a high concentration of ascorbate bec ause the oxygen radical derived from ascorbate inhibits its activity. We therefore investigated whether the inhibition of catalase activity by ascorbate could be observed in animal tissues. The catalase activit y in the tissues of guinea pigs 6h after the administration of ascorba te was lower than that in non-administered animals. When guinea pigs w ere fed diets containing 5 mg or 100 mg ascorbate/d/animal over a 90 w eeks period, a clear affect on catalase activity in the high-dose asco rbate group as compared to that in the low-dose ascorbate group was no t observed.