描述
24,25-Dihydroxyvitamin D (24R,25(OH)2D3) circulates in blood at concentrations about 1000 times higher than 1alpha,25(OH)2D3. 24-Hydroxylase is present in the proximal convoluted tubule cells of the kidney and in virtual all target cells of 1alpha,25(OH)2D3. Interestingly, 1alpha,25(OH)2D3 is a very strong inducer of 24-hydroxylase activity and 24R,25(OH)2D3 formationand is) also parathyroid hormone (PTH) regulates 24-hydroxylase activity but in a tissue specific manner, i.e. inhibitory in the kidney while a synergistic effect together with 1alpha,25(OH)2D3 is observed in osteoblasts. Generally, 24-hydroxylation has been considered the first step in the degradation pathway of 1alpha,25(OH)2D3 and 25-(OH)D3. However, through the past decades data have accumulated that 24R,25(OH)2D3 is not merely a degradation product but has effects on its own. Classic studies have demonstrated the significance of 24R,25(OH)2D3 for normal chicken egg hatchability and calcium and phosphorus homeostasis. More recently it became apparent that 24R,25(OH)2D3 also has distinct effects on cartilage in particular the resting zone cells. 24R,25(OH)2D3 stimulates osteocalcin synthesis in human osteoblasts. 24R,25(OH)2D3 plays a role in bone metabolism but that it acts in concert with 1alpha,25(OH)2D3 to obtain an optimal effect. (PMID: 11179746 ) [HMDB]
InChI标识符
InChI=1S/C27H44O3/c1-18-8-12-22(28)17-21(18)11-10-20-7-6-16-27(5)23(13-14-24(20)27)19(2)9-15-25(29)26(3,4)30/h10-11,19,22-25,28-30H,1,6-9,12-17H2,2-5H3/b20-10-,21-11+