Metabolism in vitro of 25-hydroxycholecalciferol in chicks fed on phosphorus-deficient diets.
1. Three groups of 10-days-old chicks were fed on one of three diets having phosphorus contents of 0.08 mol/kg, 0.14 mol/kg or 0.21 mol/kg. Ten days later duodenal calcium absorption by the ligated loop technique in vivo, and plasma calcium and phosphorus concentrations, were measured. In addition the metabolism in vitro of 25-hydroxycholecalciferol [25-(OH)D3] by kidney homogenates was studied. 2. In the low phosphorus group (0.08 mol/kg) calcium absorption and the activity of 25-(OH)D3-1-hydroxylase were significantly higher than those of the high phosphorus group (0.21 mol/kg). However, in the medium phosphorus group (0.14 mol/kg), calcium absorption was significantly higher although the activity of 25-(OH)D3-1-hydroxylase was not significantly higher when compared with the high phosphorus group (0.21 mol/kg). 3. It is concluded that in phosphorus deprivation, unlike in calcium deprivation, a diet very low in phosphorus is required to stimulate the renal 25-(OH)D3-1-hydroxylase activity.
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002645:Chickens / Q000378:metabolism*; D006887:Hydroxycholecalciferols / Q000378:metabolism*; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007668:Kidney / Q000201:enzymology; D008297:Male; D010758:Phosphorus / Q000097:blood / Q000172:deficiency*
D006887:Hydroxycholecalciferols; D010758:Phosphorus; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002118:Calcium