Determination of biological activity of 24,24-difluoro-1,25-dihydroxyvitamin D3 in the chick using a new method for assessing intestinal calcium uptake |
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| Authors: | B D Kabakoff N C Kendrick D Faber H F Deluca S Yamada H Takayama |
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| Institution: | 1. Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706 U.S.A.;2. Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kangawa 199-01, Japan |
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| Abstract: | Oxygen-dependent calcium uptake by chick duodenal discs has been characterized and used to assay the relative activities of 1,25-dihydroxyvitamin D3 and its 24,24-difluoro analog. The calcium uptake was found to be stimulated by low sodium (30 mm) and phosphate (0.01–0.3 mm). The rate of oxygen-dependent calcium uptake was found half-maximal at a calcium concentration of 5 mm. At a concentration of 5 mm calcium, the uptake was linear for at least 15 min with approximately a threefold stimulation by prior administration of 1,25-dihydroxyvitamin D3 (125 ng). This determination, as well as increase in serum calcium and percentage bone ash, was used to assess the biological activities of 1,25-dihydroxyvitamin D3 and its 24,24-difluoro analog. The difluoro analog is about four to five times more active than 1,25-dihydroxyvitamin D3 as measured in each of these systems. |
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| Keywords: | Author to whom correspondence should be addressed no reprints of this article will be available from authors |
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