1133 SERUM VITAMIN D BINDING PROTEIN (DBP) IN PRETERM INFANTS

Abstract

DBP is low in the cord blood of preterm infants (359±24μg/ml) while term infants (558±78μg/ml) have adult concentrations (525±24 μg/ml). To see when preterm infants develop normal concentrations of DBP and to look for any relationship to DBP's major ligand, 25-hydroxyvitamin D (25-OHD), DBP was measured by radial immunodiffusion using a rabbit antiserum in serial serum samples from 28 preterm infants, gestation 29.7±2.5wks and birthweight 1162±344gms. DBP remained low until there was a significant increase at 12wks of age (p<.01 by paired t-test). 25-OHD also increased (p<.025) at 12wks and was then correlated with serum calcium (r=.44, p<.05) and phosphorus (r=.48, p<.05). At 12wks only there were positive correlations of DBP with 25-OHD (r=.69, p<.01) and phosphorus (r= .49, p<.05). There was no correlation with gestational age or birthweight. In very preterm infants, serum albumin, ceruloplasmin and somatomedin follow a similar pattern. In 11 study infants, Lowry proteins on the same samples increased at 12wks so that DBP/gm protein remained stable. In 10 other study patients, albumin similarly increased. The changes in DBP probably reflect a maturation in the liver's ability to synthesize many proteins. The correlation with 25-OHD may represent a concurrent maturation in the liver's ability to hydroxylate vitamin D and is probably without physiological significance.

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