1,25-Dihydroxyvitamin D3 receptor in bovine thymus gland |
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Authors: | Timothy A. Reinhardt Ronald L. Horst E.Travis Littledike Donald C. Beitz |
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Affiliation: | 1. National Animal Disease Center, Agricultural Research Service, U. S. Department of Agriculture, Ames, IA 50010 USA;2. Department of Animal Science, Iowa State University, Ames, IA 50011 USA |
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Abstract: | 1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] receptor was characterized after partial purification of thymus cytosol by ammonium sulfate fractionation. The 1,25-(OH)2D3 receptor sediments at 3.7S in 5–20% sucrose gradients. The binding of 1,25-(OH)2D3 in thymic cytosol was a saturable process with high affinity (Kd = 0.12?0.48 nM) at 4°C. Competition for 1,25-(OH)2[3H]D3 receptor by nonradioactive analogs demonstrated the affinities of these analogs to be in order; 1,25-(OH)2D3 = 1,24R,25-(OH)3D3 = 1,25S,26-(OH)3D3 = 1,25R,26-(OH)3D3 > 1,25-(OH)2D3-26,23 lactone > 25-OHD3 > 23R,25-(OH)2D3 > 24R,25-(OH)2D3 > 23S,25-(OH)2D3 ? 25-OHD3-26,23 lactone. The receptor bound to DNA cellulose columns in low salt buffer and eluted as a single peak at 0.21 M KCl. These findings provide evidence that the thymus possesses a 1,25-(OH)2D3 receptor with properties indistinguishable from 1,25-(OH)2D3 receptors in other tissues. |
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Keywords: | Address correspondence to Dr. T. A. Reinhardt National Animal Disease Center ARS USDA P.O. Box 70 Ames IA 50010. |
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