Intestinal Vitamin D-dependent Calcium Binding Protein in the Chicks having Different Plasma Alkaline Phosphatase Variants

Abstract

Using chicks, of which plasma alkaline phosphatase (AP) differed in variants, the changes of vitamin D-dependent calcium binding protein (CaBP) in duodenal mucosa were observed in relation with the changes in serum Ca and P concentration and AP activity. The interaction of AP and CaBP was also observed by CaBP-coupled Sepharose 4B affinity column chromatography. Serum AP activity and P concentration were higher in F-type chicks having sialo-form of AP than in S-type chicks having desialo-form. But the differences in serum Ca and vitamin D metabolites concentration were not observed in the two groups. Concentration of soluble CaBP was found to be higher in S-type than in F-type. The binding of CaBP to AP was significantly higher in F-type than in S-type. These results suggest that the binding of CaBP to AP involves the presence of sialic acid and that the difference in AP variants results in the changes of the distribution of CaBP in the intestinal mucosa.