Duodenal calcium-binding protein (CaBP) and phosphorus deprivation in growing rats.

The present study has been undertaken to elicit the effects of a low-phosphorous diet on intestinal calcium absorption. Measurements of duodenal calcium-binding protein (CaBP), mucosal calcium, fractional calcium absorption and duodenal calcium transport capacity has been performed in growing rats fed for three weeks a low-phosphorous diet adequate in vitamin-D3. In animals on low-phosphorous diet, the mucosal concentration of CaBP measured by a quantitative competitive binding assay has increased in parallel with the mucosal calcium concentration, the fractional absorption and the calcium transport capacity. Analytical gel electrophoresis of calcium-binding protein in animals fed low-phosphorous diet has shown the presence of a protein band which would involve more than the effect of the stimulated biosynthesis of 1alpha,25-DHCC.