Ceruloplasmin oxidase activity as a biomarker of lead exposure.

The most sensitive method used in monitoring the blood lead-level is atomic absorption spectrophotometry. Its limitation due to its high cost has made delta-aminolaevulinic acid dehydratase (delta-ALAD) inhibition more popular. This work demonstrates that ceruloplasmin (Cp), the blue-colored copper containing alpha-2 globulin (alpha(2) globulin) glycoprotein in serum, can serve as a high-potential biomarker for lead exposure. Sephadex G-200 column chromatography demonstrated that lead-intoxicated patient serum transferrin and ceruloplasmin are bound to lead. The ceruloplasmin's oxidase and delta-ALAD activities are reduced when the blood-lead level increases (thresholds of 10.0 and 12.5 mug/100 mL respectively), with a correlation coefficient of -0.8643 and -0.6785 which accurately estimate a blood lead level of 74.7% and 46.0%, respectively. When the blood-lead level was less than 20 mug/100 mL, correlation coefficients of -0.5785 and -0.6963 suggested that Cp may serve as a good biomarker. Other advantages in using Cp in monitoring the blood-lead level were its stability: the enzyme was more stable at -20 degrees C, for more than 2 wk, and its practical and rapid determination procedure.