Embryonic chick intestine in organ culture: Stimulation of calcium transport by exogenous vitamin D-induced calcium-binding protein

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.

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Induction of Calcium-Binding Protein in Embryonic Chick Duodenum In Vitro: Direct Assessment of Biopotency of Vitamin D-Steroids

Vitamin D ◽

10.1007/978-1-4613-2839-1_12 ◽

1984 ◽

pp. 325-341 ◽

Cited By ~ 2

Author(s):

Robert A. Corradino

Keyword(s):

Vitamin D ◽

Calcium Binding ◽

Binding Protein ◽

Calcium Binding Protein ◽

Embryonic Chick ◽

Direct Assessment

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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.

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