Studies on calciferol metabolism: Metabolism of 25-hydroxy-Vitamin D3 by the chicken embryo |
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Authors: | June E. Bishop Anthony W. Norman |
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Affiliation: | Department of Biochemistry, University of California, Riverside, California 92502 USA |
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Abstract: | It is known that after birth of a vertebrate there is a requirement for the metabolism of Vitamin D3 (cholecalciferol) to 1,25-(OH)2-Vitamin D3 to produce the hormonally active form essential for calcium homeostasis. However it is not known whether the enzymatic capability to produce 1,25-(OH)2-D3 only appears after birth or whether it is generated in the embryo. Presented in this paper are results of studies designed to measure the production and localization of 1,25-(OH)2-D3 in the embryo. It was found that the renal enzyme, 25-OH-cholecalciferol-1-hydroxylase, which is capable of producing 1,25-(OH)2-D3, is present as early as day 9 of incubation (12 days before hatch) in White Leghorn chicks. Further, the enzyme activity increases 6-fold to a maximal level which occurs on the day of hatching. 1,25-(OH)2-D3 was shown to be produced in vivo at day 17 and was found then in low levels in the embryonic intestine and kidney. Thus we have shown that 1,25-(OH)2-D3 is made by embryonic chick kidneys and is found in low levels in embryonic chick intestine and kidney significantly before hatch. |
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