VITAMIN-C AT CONCENTRATIONS OBSERVED IN PREMATURE BABIES INHIBITS THEFERROXIDASE ACTIVITY OF CERULOPLASMIN

High concentrations of total vitamin C have been measured in the plasm a of premature infants. At these concentrations ascorbic acid inhibite d the ferroxidase activity of caeruloplasmin measured directly in vitr o. The degree of inhibition was dependent on the ratio of ascorbic aci d: caeruloplasmin. Values for the ratio of vitamin C: caeruloplasmin m easured in premature babies would be predicted to inhibit ferroxidase activity by up to at least 80%. Ferroxidase activity measured in the p lasma of premature babies increased from birth but was significantly l ower than in plasma collected from adults (<0.001). Plasma ferroxidase activity was correlated with plasma caeruloplasmin concentration and, in premature babies only, showed a negative correlation with the rati o of vitamin C to caeruloplasmin. High levels of vitamin C in prematur e babies may compromise antioxidant mechanisms and exacerbate oxidant damage.