A Competitive Protein Binding Assay for Plasma 25-Hydroxyvitamin D₃ in Normal Children

Abstract

In order to determine the plasma level of 25-hydroxyvitamin D₃ (25-OH-D₃) in Japanese children by the competitive protein binding assay, we studied binding proteins in D-deficient rats, and obtained the following results. 1) By using serum and kidney cytosol of D-deficient rats, we could obtain a standard curve with high sensitivity and accuracy which enabled us to determine the 25-OH-D₃ level ranging from 0.5 to 5.0ng. 2) The plasma 25-OH-D₃ level was found to be 21.6±10.1ng/ml (n=17) in healthy infants and children from 1 to 15 year-old, and 11.4±8.6ng/ml (n=27) in mature neonates up to 2 days after delivery.