Effect of Vitamin D and Dietary Content of Calcium and Phosphorus on Protein Synthesis in Rat Duodenal Mucosa.

摘要

Forty-eight hours after administration of vitamin D to D-deficient rats, there was less total protein in the mucosa of the duodenum than in comparable rats not treated with the vitamin. During this time there was a shift in the proportion of protein contributed by each of the fractions measured. Generally, the soluble protein fraction diminished while the nuclear debris fraction increased. For those fed diet 1 (1.2% Ca: 0.02% P), vitamin D increased the proportion of mitochondrial and microsomal protein, while those fed diet 2 (0.0% Ca: 0.3% P) showed no marked change in these particulate fractions. These data suggest that vitamin D causes an increased synthesis of new epithelial cells in the duodenum while at the same time decreasing the time required for their maturation and sloughing. Gel electrophoretic separation of the soluble proteins from the mucosa suggested the presence of a pre-calcium binding protein (pre-CaBP) in rats on both diets before they were treated with vitamin D. Also, the D-deficient rats fed diet 2 had a band which appeared in the same region as CaBP. When vitamin D was administered, the pre-CaBP disappeared in both groups while the CaBP was evident in both groups. Labeled amino acids did not contribute any significant radioactivity to the pre-CaBP or CaBP region indicating that the CaBP formed during the 48-hour test period did not require de novo protein synthesis.