Increased 1,25-dihydroxyvitamin D3 synthesis in rats fed a high-phosphorus diet |
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Authors: | G. M. Siu H. H. Draper |
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Affiliation: | (1) Department of Nutrition, College of Biological Science, University of Guelph, N1G 2W1 Guelph, Ontario, Canada |
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Abstract: | Summary Rats fed vitamin D-deficient diets containing 0.6% Ca and 0.3%, 0.6%, 1.2%, or 1.8% P exhibited progressive increments of hypocalcemia and hyperphosphatemia. In vitro assay of 25-hydroxyvitamin D3-1-α-hydroxylase (1-α-hydroxylase) activity in isolated kidney cortical mitochondria showed that hyperphosphatemia in the presence of hypocalcemia was associated with an increase in enzyme activity. The results indicate that the stimulation of 1-α-hydroxylase associated with depressed plasma Ca in rats fed a high-P diet overrides any inhibition of the enzyme that may be caused by excess plasma phosphate. |
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Keywords: | 1,25-Dihydroxyvitamin D3 Hypocalcemia Hyperphosphatemia |
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