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The Effects of 24R, 25‐Dihydroxyvitamin D3 and 24S, 25Dihydroxyvitamin D3 on Phosphate Transport in Vivo
Author(s) -
Meng Yu,
Nemere Ilka
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.649.4
Subject(s) - in vivo , endocrinology , chemistry , medicine , stimulation , absorption (acoustics) , vitamin d and neurology , steroid hormone , phosphate , hormone , vitamin , steroid , biology , biochemistry , microbiology and biotechnology , physics , acoustics
The steroid hormone 1, 25‐dihydroxyvitamin D 3 [1,25D 3 ] rapidly stimulates the uptake of phosphate in isolated chick intestinal cells, while 24,25‐dihydroxyvitamin D 3 [24,25D 3 ] inhibits the rapid stimulation by 1,25D 3 . in isolated intestinal cells and perfused duodenal loops. Studies were undertaken to determine if 24,25D 3 had a similar effect in vivo. 24,25D 3 has two isomers which are 24R, 25dihydroxyvitamin D 3 [24R,25D 3 ] and 24S, 25dihydroxyvitamin D 3 [24S,25D 3 ]. We studied these two isomers separately and tested them over a time course of 1, 5, 10, 15 and 18 h after steroid using chicks on regular diet, but fasted, and chicks on a lower vitamin D diet. All chicks were anesthetized prior to surgical exposure of the duodenal loop and injection of H 3 32 PO 4 in buffer into the lumen. An initial study determined that 3 to 9 min of absorption in vivo was in a linear range, as judged by serum levels of radioactivity. Chicks were then injected IM with either 200 μg 24R,25D 3 , 20 μg 24S,25D 3 or vehicle (1–18 h prior to experimentation) within the same time course studies. The isomers had different effects on phosphate absorption: 24R,25D 3 had a hypophosphatemic effect in vivo in which serum levels at 5, 15 and 18 h had decreased to 42%, 39% and 43%, respectively, ( P < 0.05) compared with controls. In contrast, 24S, 25(OH) 2 D 3 stimulated intestinal phosphate absorption at the 5h time point by 64%, but had no effect at the other time points tested. Supported by Agriculture and Food Research Initiative Competitive Grant no. 2010‐65206‐20652 from the USDA National Institute of Food and Agriculture.