Rat albumin inhibits the formation of apoceruloplasmin during storage

Purified rat ceruloplasmin is extraordinarily unstable in storage at -70 de grees C. In a 20 mM phosphate buffer, pH 7.0, the ferroxidase and amine oxi dase of ceruloplasmin are over 90% inactivated within two weeks. Holocerulo plasmin stored for three months in a 20 mM barbital buffer (or acetate buff er), pH 7.0 (or pH 5.5) was transformed into an apo-protein and amine (o-di anisidine) oxidase of ceruloplasmin was inactivated by 50-55%. The patterns of ferroxidase activity loss were similar to those of amine oxidase activi ty loss. On the contrary, when holoceruloplasmin was mixed with rat serum a lbumin, transformation into apoceruloplasmin was significantly prevented in a 20 mM barbital buffer, pH 7.0 (or 20 mM acetate buffer, pH 5.5). Consequ ently, ferroxidase and amine oxidase activities of ceruloplasmin were not i nactivated and the immunochemical reactivity was not changed. These results can be applied for laboratorial and clinical purposes.