renal/urinary system
• homozygotes excrete ~6 times more Ca2+ in their urine, reaching a urinary Ca2+ concentration of up to 20 mM relative to 6 mM observed in wild-type littermates
• hypercalciuria persists even when homozygotes are placed on a Ca2+-deficient diet for 1 week
• in contrast to excessive renal Ca2+ wasting, total excretion of Na+ and K+ remains unaffected
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• homozygotes exhibit calciuresis as a result of reduced active Ca2+ reabsorption within the early part of the distal convoluted renal tubules
• quantitative free-flow collection of tubular fluid revealed unaffected Ca2+ reabsorption up to the last loop of proximal renal tubules
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• mutant urine is significantly more acidic than control urine
• neutralization of the acidic urine results in the development of large crystals
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• homozygotes display a significant increase in urinary phosphate excretion relative to wild-type mice (512 30 mol and 327 25 mol per 24 hrs per three mice, respectively)
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• at 8-9 weeks of age, homozygotes exhibit polyuria relative to wild-type and heterozygous control mice
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homeostasis/metabolism
N |
• homozygotes display normal serum Ca2+ and K+ concentrations, despite renal Ca2+ wasting and hyperphosphaturia
• homozygotes display normal parathyroid hormone (PTH) levels, despite significantly elevated serum 1,25-(OH)2D3 levels
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• homozygotes exhibit calciuresis as a result of reduced active Ca2+ reabsorption within the early part of the distal convoluted renal tubules
• diminished active Ca2+ reabsorption in the kidney results in compensatory intestinal hyperabsorption, as shown by measuring changes in serum 45Ca2+ at early time points after oral gavage
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• homozygotes excrete ~6 times more Ca2+ in their urine, reaching a urinary Ca2+ concentration of up to 20 mM relative to 6 mM observed in wild-type littermates
• hypercalciuria persists even when homozygotes are placed on a Ca2+-deficient diet for 1 week
• in contrast to excessive renal Ca2+ wasting, total excretion of Na+ and K+ remains unaffected
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• homozygotes exhibit calciuresis as a result of reduced active Ca2+ reabsorption within the early part of the distal convoluted renal tubules
• quantitative free-flow collection of tubular fluid revealed unaffected Ca2+ reabsorption up to the last loop of proximal renal tubules
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• homozygotes display elevated serum levels of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) relative to wild-type mice
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• mutant urine is significantly more acidic than control urine
• neutralization of the acidic urine results in the development of large crystals
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• homozygotes display a significant increase in urinary phosphate excretion relative to wild-type mice (512 30 mol and 327 25 mol per 24 hrs per three mice, respectively)
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skeleton
• homozygotes display a significantly reduced polar moment of inertia (MOI), indicating an abnormal geometrical distribution and reduced mechanical properties of the diaphyseal bone (femur)
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• homozygotes display significant changes in bone structure, with no significant alterations in bone length or body weight relative to wild-type mice
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• homozygotes display a significant increase in the number and surface area of osteoclasts per bone surface area, as determined in femoral metaphyses
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• homozygotes display a significant reduction in cortical volume, cortical bone volume fraction, and cortical thickness relative to wild-type mice
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• homozygotes display a significant reduction of trabecular bone thickness in the femoral head
• however, the trabecular bone volume fraction, trabecular number, connectivity density, and structure model index remain unaffected in the femoral head
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hematopoietic system
• homozygotes display a significant increase in the number and surface area of osteoclasts per bone surface area, as determined in femoral metaphyses
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immune system
• homozygotes display a significant increase in the number and surface area of osteoclasts per bone surface area, as determined in femoral metaphyses
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