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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
2
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pubmed:dateCreated |
1984-9-5
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pubmed:abstractText |
Renal mitochondria from mutant hypophosphatemic male mice (Hyp/Y) fed a vitamin D-deficient, low calcium diet synthesize significantly less 1,25-dihydroxyvitamin D3 than mitochondria from normal male (+/Y) littermates on the same diet. Kinetic studies reveal that maximum velocity (Vmax) for 25-hydroxyvitamin D3-1-hydroxylase (1-hydroxylase) is lower in Hyp/Y relative to +/Y mice (0.21 +/- 0.02 vs. 1.06 +/- 0.12 pmol/mg protein X min) whereas the apparent Michaelis-Menten constant (Km) for the reaction is not different in both genotypes (0.55 +/- 0.05 vs. 0.50 +/- 0.08 microM). The presence of an inhibitor for 1-hydroxylase activity in renal mitochondria of Hyp/Y mice was ruled out by estimating enzyme activity in mixtures of renal mitochondria from +/Y and Hyp/Y mice. Phosphate in the incubation medium stimulated 1-hydroxylase activity in +/Y mitochondria. In Hyp/Y mice, the stimulation achieved was smaller in magnitude and the added phosphate did not restore mutant 1-hydroxylase activity to normal. The vitamin D-deficient, low calcium diet led to a significant and comparable increase in serum PTH and urinary excretion of cAMP in +/Y and Hyp/Y, suggesting that the mutant strain had an appropriate PTH response to the diet-induced fall in serum calcium. Furthermore, the fractional excretion index of phosphate which is significantly greater in Hyp/Y than +/Y mice fed the control diet increased 3-fold in both genotypes fed the vitamin D-deficient, low calcium diet. These results suggest that the abnormal renal 1-hydroxylase response in Hyp mice is not the result of generalized renal resistance to PTH in the mutant strain and suggest that the defect in Hyp/Y mice may reside at a regulatory step subsequent to cAMP production.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
AIM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/25-Hydroxyvitamin D3...,
http://linkedlifedata.com/resource/pubmed/chemical/Calcium,
http://linkedlifedata.com/resource/pubmed/chemical/Cyclic AMP,
http://linkedlifedata.com/resource/pubmed/chemical/Phosphates,
http://linkedlifedata.com/resource/pubmed/chemical/Steroid Hydroxylases
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pubmed:status |
MEDLINE
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pubmed:month |
Aug
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pubmed:issn |
0013-7227
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
115
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
634-9
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pubmed:dateRevised |
2003-11-14
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pubmed:meshHeading |
pubmed-meshheading:6086274-25-Hydroxyvitamin D3 1-alpha-Hydroxylase,
pubmed-meshheading:6086274-Animals,
pubmed-meshheading:6086274-Biomechanics,
pubmed-meshheading:6086274-Calcium,
pubmed-meshheading:6086274-Cyclic AMP,
pubmed-meshheading:6086274-Female,
pubmed-meshheading:6086274-Hypophosphatemia, Familial,
pubmed-meshheading:6086274-Kidney,
pubmed-meshheading:6086274-Kinetics,
pubmed-meshheading:6086274-Male,
pubmed-meshheading:6086274-Mice,
pubmed-meshheading:6086274-Mice, Mutant Strains,
pubmed-meshheading:6086274-Mitochondria,
pubmed-meshheading:6086274-Phosphates,
pubmed-meshheading:6086274-Sex Chromosome Aberrations,
pubmed-meshheading:6086274-Steroid Hydroxylases,
pubmed-meshheading:6086274-Vitamin D Deficiency,
pubmed-meshheading:6086274-X Chromosome
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pubmed:year |
1984
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pubmed:articleTitle |
Investigation of the mechanism for abnormal renal 25-hydroxyvitamin D3-1-hydroxylase activity in the X-linked Hyp mouse.
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pubmed:publicationType |
Journal Article
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