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United States Department of Agriculture

Agricultural Research Service

Title: A Comparison of the Relative Effects of 1,24(oh)2d2, 1,24(oh)2d3, and 1,25(oh)2d3 on Calcium Metabolism in the Rat.

item Horst, Ronald
item Prapong, Siriwan - IOWA STATE UNIVERSITY
item Reinhardt, Timothy
item Koszewski, Nick - UNIV KENTUCKY MED COLL
item Knutson, Joyce - BONE CARE INTL
item Bishop, Charles - BONE CARE INTL

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 29, 1997
Publication Date: N/A

Technical Abstract: The present experiments were conducted to compare the relative hypercalcuric and hypercalcemic activities of 1,24(OH)2D2, 1,24(OH)2D3, and 1,25(OH)2D3 in 7-week-old rats. The rats were dosed orally with each sterol for 7 days at a rate of 1ng/g BW/day. We also monitored the ability of these compounds to up-regulate the 24-hydroxylase mRNA and to evoke modifications in the VDR/RXR heterodimer conformation. Plasma calcium was elevated in the rats treated with 1,24(OH)2D3 and 1,25(OH)2D3, but not in the 1,24(OH)2D2-dosed rats. Urinary calcium was significantly elevated in all groups. The order of hypercalcuric activity was 1,25(OH)2D3 > 1,24(OH)2D3 > 1,24(OH)2D2. Duodenal 24-hydroxylase mRNA was elevated in all groups; however, the elevations were significantly higher in the 1,24(OH)2D3 and 1,25(OH)2D3 groups. Kidney 24-hydroxylase was also significantly elevated in 1,24(OH)2D3- and 1,25(OH)2D3- treated rats. Recombinant human VDR extracts were incubated with saturating concentrations of 1,24(OH)2D2 and 1,25(OH)2D3, and subsequently analyzed by EMSA.

Last Modified: 4/18/2015
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