The metabolism of fetuin and asialo-fetuin by established lines of cells in culture [proceedings].

amount of peroxychromate added was calculated to yield about twice as much singlet oxygen as substrate. Clearly the oxidation process is highly efficient. In a second series of experiments we examined the oxidation of aqueous dispersions of soya-bean phosphatidylcholine. The substrate was dried from chloroform/methanol (2: 1, v/v) under N, and dispersed in water (5mg/ml) by ultrasonication. Portions (10ml) of the phospholipid dispersion were incubated with 500mg of potassium peroxychromate under the same conditions as that for Tween 80. Analyses of the fatty acid methyl esters prepared at various reaction times showed that the rate of loss of the unsaturated fatty acyl residues of the phospholipid was considerably lower than the rate of oxidation of Tween 80. Thus after 24 h incubation the ratio of palmitate, used as the internal standard for the reaction, to linoleate had increased only by about 15%. The explanation for this effect may lie in the manner of presentation of the substrate, i.e. a miceller structure in the case of Tween 80 and a lamellar vesicle of phospholipid. Further studies are required to examine this point and to identify the reaction products produced during the oxidation process.