Regulation by Dietary Calcium of Vitamin D-Dependent Calcium-Binding Protein and Active Calcium Transport in the Small Intestine of Lactating Rats*

This study aimed to investigate the mechanism of active calcium transport in the chick embryonic chorioallantoic membrane (CAM) by assessing the functional involvement of three previously identified, putative components of the transport pathway. These components are a calcium-binding protein (CaBP), Ca2+-activated ATPase and carbonic anhydrase. Using specific reagents, including antibodies and enzyme inhibitors in vivo and in vitro in CAM calcium uptake assays, it was shown that these biochemically identified components were all functionally involved. The results of these studies also indicate that active calcium uptake by the CAM requires the presence of the CaBP on the cell surface in a laterally mobile manner, while carbonic anhydrase appeared to be a cytosolic component. We further analysed the subcellular location of the calcium-uptake activity by gel filtration and density-gradient fractionation of cell-free microsomes of the CAM and the results suggest that this activity is associated with the plasma membrane.

Download Full-text

The response of the small intestine to vitamin D. Correlation between calcium-binding-protein production and increased calcium absorption

Biochemical Journal ◽

10.1042/bj1440339 ◽

1974 ◽

Vol 144 (2) ◽

pp. 339-346 ◽

Cited By ~ 29

Author(s):

J S Emtage ◽

D E M Lawson ◽

E Kodicek

Keyword(s):

Vitamin D ◽

Protein Synthesis ◽

Small Intestine ◽

Calcium Binding ◽

Protein Production ◽

Calcium Absorption ◽

Binding Protein ◽

Calcium Binding Protein ◽

Intestinal Cell ◽

Stimulation Of

1. The synthesis of calcium-binding protein, a protein produced in the small intestine in response to vitamin D, was investigated with a view to determining whether calcium-binding-protein production could be correlated with the stimulation of calcium absorption by vitamin D. 2. A radioimmunological assay, which can quantitatively estimate calcium-binding-protein concentrations as low as 1μg/g wet wt., was used to detect the synthesis of soluble calcium-binding protein. 3. When used on intestinal supernatants from chicks dosed with vitamin D, calcium-binding protein was not detectable at 8h but was present after 12h at a concentration of 8.6μg/g wet wt.; in agreement with this an increase in calcium absorption due to vitamin D was detected at 12h but not at 8h. 4. The synthesis of calcium-binding protein was also monitored directly by making use of the ability of the iodinated antiserum to bind specifically to nascent calcium-binding protein chains on intestinal polyribosomes; in this way calcium-binding-protein synthesis could be detected 8h after dosage with vitamin D. Further, the binding reaction indicated a near linear increase in the calcium-binding-protein-synthesizing capacity over a 16h period. 5. From the amount of calcium-binding protein present 12 and 24h after vitamin D administration it is calculated that calcium-binding-protein mRNA is produced at approx. 1mol/min per intestinal cell. 6. It is concluded that the high correlation between the initiation of calcium-binding-protein synthesis and the stimulation of calcium absorption by vitamin D strengthens the proposal that calcium-binding protein plays an important role in calcium transport.

Download Full-text

Effect of Dietary Calcium and Phosphorus Depletion on Vitamin D Metabolism and Calcium Binding Protein in the Growing Pig

Hormone and Metabolic Research ◽

10.1055/s-2007-1013456 ◽

1985 ◽

Vol 17 (02) ◽

pp. 78-81 ◽

Cited By ~ 20

Author(s):

B. Sommerville ◽

E. Maunder ◽

R. Ross ◽

A. Care ◽

R. Brown

Keyword(s):

Vitamin D ◽

Calcium Binding ◽

Binding Protein ◽

Dietary Calcium ◽

Calcium Binding Protein ◽

Vitamin D Metabolism ◽

Growing Pig ◽

Calcium And Phosphorus ◽

Phosphorus Depletion

Download Full-text

The response of the small intestine to vitamin D. Isolation and properties of chick intestinal polyribosomes

Biochemical Journal ◽

10.1042/bj1400239 ◽

1974 ◽

Vol 140 (2) ◽

pp. 239-247 ◽

Cited By ~ 27

Author(s):

J. Spencer Emtage ◽

D. Eric M. Lawson ◽

Egon Kodicek

Keyword(s):

Vitamin D ◽

Small Intestine ◽

Rat Liver ◽

Liver Cell ◽

Calcium Binding ◽

De Novo ◽

Binding Protein ◽

Calcium Binding Protein ◽

Intestinal Cell ◽

Polypeptide Chains

Undegraded polyribosome preparations may be obtained from chick intestinal mucosa if ribonuclease activity is strictly controlled. This is best achieved by homogenization of the mucosa directly in rat liver cell-sap. 2. The extent of amino acid incorporation by chick intestinal polyribosomes is greatly influenced by the source of the cell-sap. Sephadex-treated intestinal cell-sap caused impaired incorporation and release of completed polypeptide chains, whereas Sephadex-treated rat liver cell-sap promoted the polymerization of up to 90 amino acids per ribosome. Under optimum conditions 30–35% of the nascent polypeptide chains are completed and released. 3. The preparation of an antiserum against the calcium-binding protein formed in response to vitamin D is described. It is shown that the antiserum is highly specific for calcium-binding protein. 4. This antiserum was used to investigate the ability of chick intestinal polyribosomes to synthesize calciumbinding protein. Only polyribosomes from chicks receiving vitamin D have the ability to synthesize calcium-binding protein. Moreover, the product formed in vitro has the same electrophoretic mobility as calcium-binding protein synthesized in vivo. 5. It is concluded that one of the main functions of vitamin D in the small intestine is to induce the synthesis de novo of calcium-binding protein.

Download Full-text

Intestinal vitamin D-induced calcium-binding protein: time-course of immunocytological localization following 1,25-dihydroxyvitamin D3.

Journal of Histochemistry & Cytochemistry ◽

10.1177/31.3.6687473 ◽

1983 ◽

Vol 31 (3) ◽

pp. 426-432 ◽

Cited By ~ 12

Author(s):

A N Taylor

Keyword(s):

Vitamin D ◽

Calcium Binding ◽

Calcium Transport ◽

Time Course ◽

Binding Protein ◽

Calcium Binding Protein ◽

Dihydroxyvitamin D3 ◽

Migration Rates ◽

1,25 Dihydroxyvitamin D3 ◽

Free Cells

The vitamin D-induced calcium-binding protein (CaBP) was localized in histological sections of chick duodenum using the peroxidase-antiperoxidase immunocytochemical technique. The time-course of appearance of CaBP in rachitic chicks was investigated from 0 to 120 hr after stimulation by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). CaBP was not routinely detected at 0 hr after 1,25(OH)2D3 administration. CaBP was first noted in some, but not all, of the samples taken 2 hr following 1,25(OH)2D3 and was detected in all 2 1/2 hr samples. The number of CaBP-containing absorptive cells and the apparent CaBP concentration both increased to a maximum at about 16-24 hr. At later times, as CaBP free cells migrated up the villi, the CaBP-containing cells decreased in number, but even at 120 hr post 1,25(OH)2D3 dose there were significant numbers of CaBP-containing cells present. The relationships between time-course of CaBP location on intestinal villi, enterocyte migration rates, and the time-course of 1,25(OH)2D3 stimulated intestinal calcium transport are discussed.

Download Full-text