scholarly journals 1,25-Dihydroxyvitamin D3 Rapidly Stimulates the Solvent Drag–Induced Paracellular Calcium Transport in the Duodenum of Female Rats

2008 ◽  
Vol 58 (5) ◽  
pp. 297-307 ◽  
Author(s):  
Kukiat Tudpor ◽  
Jarinthorn Teerapornpuntakit ◽  
Walailuk Jantarajit ◽  
Nateetip Krishnamra ◽  
Narattaphol Charoenphandhu
Keyword(s):  
Calcium Transport ◽  
Female Rats ◽  
Solvent Drag ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3

Biological activity of 24,24-difluoro-1,25-dihydroxyvitamin D3

1983 ◽  
Vol 244 (2) ◽  
pp. E159-E163
Author(s):  
S. Okamoto ◽  
Y. Tanaka ◽  
H. F. DeLuca ◽  
Y. Kobayashi ◽  
N. Ikekawa
Keyword(s):  
Biological Activity ◽  
Calcium Transport ◽  
Plasma Calcium ◽  
Epiphyseal Plate ◽  
Dihydroxyvitamin D3 ◽  
Responsive Systems ◽  
1,25 Dihydroxyvitamin D3 ◽  
Bone Calcium ◽  
Calcium And Phosphorus

The biological activity of 24,24-difluoro-1,25-dihydroxyvitamin D3 was compared with 1,25-dihydroxyvitamin D3 in the rat. The 24,24-difluoro-1,25-dihydroxyvitamin D3 has a potency of approximately 5-10 times that of 1,25-dihydroxyvitamin D3 in the known in vivo vitamin D responsive systems. These systems include intestinal calcium transport, bone calcium mobilization, calcification of epiphyseal plate cartilage, and elevation of plasma calcium and phosphorus concentrations. Thus, 24,24-difluoro-1,25-dihydroxyvitamin D3 is the first known analogue with higher potency than 1,25-dihydroxyvitamin D3 in vivo.

Effects of 1,25-dihydroxyvitamin D3 on colonic calcium transport in vitamin D-deficient and normal rats

1984 ◽  
Vol 246 (3) ◽  
pp. G268-G273
Author(s):  
M. J. Favus ◽  
C. B. Langman
Keyword(s):  
Vitamin D ◽  
Calcium Transport ◽  
Calcium Absorption ◽  
Biological Response ◽  
Vehicle Control ◽  
Normal Diet ◽  
Dihydroxyvitamin D3 ◽  
Vitamin D Intake ◽  
1,25 Dihydroxyvitamin D3

To determine whether prior vitamin D intake influences the intestinal calcium absorptive action of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], we measured in vitro the two unidirectional transepithelial fluxes of calcium across descending colon segments from rats fed either a vitamin D-deficient or normal diet and injected with either 10, 25, or 75 ng of 1,25(OH)2D3 or vehicle alone. Vitamin D deficiency abolished net calcium absorption [J net, -2 +/- 2 vs. 12 +/- 2 (SE) nmol X cm-2 X h-1, P less than 0.001], and 10 ng of 1,25(OH)2D3 raised J net to levels found in normal rats. Larger doses (25 and 75 ng) increased J net above levels in normal rats given the same dose. In normal rats only 75 ng of 1,25(OH)2D3 increased calcium J net above vehicle control values (12 +/- 2 vs. 38 +/- 4 nmol X cm-2 X h-1, P less than 0.001). Circulating 1,25(OH)2D3 measured by radioreceptor assay was well correlated with calcium transport. For each dose of 1,25(OH)2D3 higher serum 1,25(OH)2D3 levels were reached in vitamin D-deficient rats. Only the 75-ng dose increased circulating 1,25(OH)2D3 and colonic calcium transport in normal rats. Intravenous [3H]-1,25(OH)2D3 disappeared more rapidly from the circulation of normal rats, suggesting that accelerated metabolic degradative processes for 1,25(OH)2D3 may be present in normal but not in vitamin D-deficient rats and may account for the lack of a biological response to 1,25(OH)2D3 in normal animals.

Effect of 1,25-dihydroxyvitamin D3 on calcium absorption in the colon of healthy humans

1984 ◽  
Vol 247 (2) ◽  
pp. G189-G192 ◽  
Author(s):  
W. C. Grinstead ◽  
C. Y. Pak ◽  
G. J. Krejs
Keyword(s):  
Short Bowel Syndrome ◽  
Calcium Transport ◽  
Calcium Absorption ◽  
Calcium Deficiency ◽  
Entire Colon ◽  
Dihydroxyvitamin D3 ◽  
Short Bowel ◽  
1,25 Dihydroxyvitamin D3 ◽  
Healthy Humans ◽  
Perfusion Studies

Calcium absorption in patients with short bowel syndrome is significantly higher when the colon is left intact. To study calcium transport in the large bowel, we investigated whether exogenous 1,25-dihydroxyvitamin D3 [1,25(OH2)D3] can induce or enhance colonic calcium absorption in healthy subjects ingesting a normal diet. Steady-state colon perfusion studies were performed before and after 1 wk of 1,25(OH)2D3 administration (2 micrograms/day, 10 subjects). Serum 1,25-dihydroxyvitamin D concentration rose from 23.0 +/- 2.2 to 39.5 +/- 4.3 pg/ml (mean +/- SE, P less than 0.01). In the basal state the mean net movement of calcium was not significantly different from zero when a 5 mM calcium gluconate solution was perfused (100 +/- 84 mumol X h-1 X entire colon secreted-1). Vitamin D administration resulted in a significant change toward calcium absorption (106 +/- 47 mumol X h-1 X entire colon absorbed-1, P less than 0.02). 1,25(OH)2D3 had no effect on colonic magnesium, phosphate, water, and electrolyte movement. This study demonstrates that in healthy humans exogenous 1,25(OH)2D3 can change colonic calcium movement toward absorption. We suspect that similar changes in colonic calcium transport are caused by endogenous 1,25(OH)2D3 when calcium deficiency has occurred in short bowel syndrome.

Duodenal and ileal calcium absorption in the rat and effects of vitamin D

1983 ◽  
Vol 244 (6) ◽  
pp. G695-G700 ◽  
Author(s):  
D. Pansu ◽  
C. Bellaton ◽  
C. Roche ◽  
F. Bronner
Keyword(s):  
Vitamin D ◽  
Calcium Binding ◽  
Calcium Transport ◽  
Calcium Absorption ◽  
Cytosolic Calcium ◽  
Chemical Gradient ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Loop Procedure ◽  
Proximal Intestine

An in situ ligated loop procedure was applied to dissect transmural calcium transport in the intestine into two components, a saturable and a nonsaturable process. The existence of two such processes was confirmed in the duodenum, but ileal calcium transport was devoid of the saturable component. There was a small saturable component in the upper jejunum. The level of CaBP, the vitamin D-dependent cytosolic calcium-binding protein (Mr, approximately or equal to 9,000), corresponded to the magnitude of the saturable component. No CaBP was detected in the ileum. Vitamin D dependence of the saturable component was established by inducing it in the duodenum of vitamin D-deficient animals following intraperitoneal injection of 1,25-dihydroxyvitamin D3. In these same animals, conversely, the ileum did not respond to exogenous 1,25-dihydroxyvitamin D3. This confirms the absence in the ileum of the saturable component of transmural calcium movement and the fact that the nonsaturable component is not vitamin D dependent. Everted sac experiments also showed that duodenal sacs from vitamin D-replete or -repleted animals transported calcium against a chemical gradient, whereas ileal sacs did not. Vitamin D regulation of intestinal calcium absorption thus occurs only in the proximal intestine, even though calcium is absorbed down its chemical gradient all along the small intestine.

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