Vitamin D

MacIntyre, I.; Evans, Imogen M. A.; Larkins, R. G.

doi:10.1111/j.1365-2265.1977.tb01997.x

Cited by 15 publications

(7 citation statements)

References 63 publications

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“…The changes, with time, on the magnesium-deficient diet were identical to those previously described, up to 80 to 90 days (7). Continued exposure to the magnesiumdeplete diet beyond that time produced no further degree of depletion but did lead to some deaths.…”

Section: Assessment Of Tissue Magnesium Statussupporting

confidence: 78%

“…Plasma magnesium is easy to measure but does not always correlate with tissue magnesium, which may be the important factor in determining toxicity. With dietary magnesium depletion, plasma magnesium falls before there are measurable changes in tissue magnesium (7) and tissue magnesium depletion can occur in the absence of low levels of plasma magnesium (8). Despite severe magnesium depletion, as assessed by bone content, there may be no change (brain) or relatively little change (muscle, heart) (7) in other tissues.…”

Section: Introductionmentioning

confidence: 99%

“…With dietary magnesium depletion, plasma magnesium falls before there are measurable changes in tissue magnesium (7) and tissue magnesium depletion can occur in the absence of low levels of plasma magnesium (8). Despite severe magnesium depletion, as assessed by bone content, there may be no change (brain) or relatively little change (muscle, heart) (7) in other tissues. While the absence of a measurable change in magnesium content of a specific tissue, in the presence of a fall in plasma and bone magnesium, may mean that the tissue has conserved magnesium, it does not exclude depletion of a small and possibly important compartment within that tissue.…”

Section: Introductionmentioning

confidence: 99%

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Problems in the assessment of magnesium depletion in the rat byin vivo³¹P NMR

Adam

Craik

Hall

et al. 1988

Magnetic Resonance in Med

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Prior in vitro studies, utilizing 31P nuclear magnetic resonance (31P NMR) to measure the chemical shift (sigma) of beta-ATP and lengthening of the phosphocreatine spin-spin (T2) relaxation time, suggested an assessment of their efficacy in measuring magnesium depletion in vivo. Dietary magnesium depletion (Mg2+ decreases) produced markedly lower magnesium in plasma (0.44 vs 1.13 mmol/liter) and bone (130 vs 190 mumol/g) but much smaller changes in muscle (41 vs 45 mumol/g, P less than 0.01), heart (42.5 vs 44.6 mumol/g), and brain (30 vs 32 mumol/g). NMR experiments in anesthetized rats in a Bruker 7-T vertical bore magnet showed that in Mg2+ decreases rats there was a significant change in brain beta-ATP shift (16.15 vs 16.03 ppm, P less than 0.05). These chemical shifts gave a calculated free [Mg2+] of 0.71 mM (control) and 0.48 mM (Mg2+ decreases). In muscle the change in beta-ATP shift was not significant (Mg2+ decreases 15.99 ppm, controls 15.96 ppm), corresponding to a calculated free Mg2+ of 0.83 and 0.95 mM, respectively. Phosphocreatine T2 (Carr-Purcell, spin-echo pulse sequence) was no different with Mg2+ decreases in muscle in vivo (surface coil) (Mg2+ decreases 136, control 142 ms) or in isolated perfused hearts (Helmholtz coil) (control 83, Mg2+ decreases 92 ms). 31P NMR is severely limited in its ability to detect dietary magnesium depletion in vivo. Measurement of beta-ATP shift in brain may allow studies of the effects of interaction in group studies but does not allow prediction of an individual magnesium status.

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Section: Assessment Of Tissue Magnesium Statussupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Problems in the assessment of magnesium depletion in the rat byin vivo³¹P NMR

Adam

Craik

Hall

et al. 1988

Magnetic Resonance in Med

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“…Physiological regulation of vitamin D activity is exerted mainly at the level of production of the highly active renal metabolite 1,25-dihydroxy-vitamin D, [ 1,,D,] from 25-hydroxy-vitamin D, [25-(OH)D,l, the major circulating form. The regulation of 25-hydroxy-vitamin D-1 a-hydroxylase [25-(OH)D-1 a-hydroxylasel has been intensively studied and many agents including calcium and phosphate, cyclic nucleotides, parathyroid hormone and prolactin, and 1,25-(OH),D, itself are now known to alter its activity (MacIntyre et al, 1977;Larkins, MacAuley, Rapoport, Martin, Tulloch, Byfield, Matthews & MacIntyre, 1974).…”

Section: Introductionmentioning

confidence: 97%

Regulation of 25-Hydroxy-Vitamin D-1α-Hydroxylase in Chick Isolated Renal Tubules: Effects of Prostaglandin E2, Frusemide and Acetylsalicylic Acid

et al. 1981

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1. Isolated renal tubules were prepared from vitamin D-deficient chicks. The effects of added prostaglandin E2 (PGE2) and agents which modify prostaglandin metabolism on the metabolism of 25-hydroxy-vitamin D3 were studied. 2. Frusemide (0.1 mmol/l) raised the prostaglandin E (PGE) content of the tubule incubation medium; it significantly increased 1,25-dihydroxy-vitamin D3 [1,25-(OH)2D3] production from 25-hydroxy-vitamin D3 [25-(OH)D3] and significantly inhibited the net production of 24,25-dihydroxy-vitamin D3 [24,25-(OH)2D3]. 3. Acetylsalicylic acid (aspirin; 0.1 mmol/l) decreased the PGE content of the tubule incubation medium and significantly inhibited 1,25-(OH)2D3 production. 4. In the presence of 1,25-(OH)2D3, 4 h exposure of tubules from vitamin D-deficient chicks to concentrations of PGE2 between 2.8 X 10(-6) and 2.8 X 10(-8) mol/l significantly enhanced 1,25-(OH)2D3 production. 5. It is concluded that, in view of the effects of modulation of endogenous prostaglandin levels by frusemide in aspirin, and the stimulatory effect of exogenous PGE2, prostaglandins should be considered potential regulators of the renal 25-hydroxy-vitamin D-1 alpha-hydroxylase [25-(OH)D-1 alpha-hydroxylase] enzyme.

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“…This defect, which is responsible for Send offprint requests to A. Caniggia at the above address. a chronic calcium deficiency, could be an important factor in the pathogenesis of postmenopausal osteoporosis [10,11].Since 1,25-dihydroxycholecalciferol (1,25(OH)2-D3) is an important regulator of calcium absorption [12], the attention of researchers has been particularly focused on this metabolite. On the contrary, few studies have been performed concerning 25-hydroxyvitamin D 1 (25-OHD) serum levels in patients with osteoporosis.…”

mentioning

confidence: 99%

Serum levels of 25-hydroxyvitamin D in postmenopausal osteoporosis

et al. 1981

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Serum concentrations of 25-hydroxy-vitamin D were measured in a group of women with symptomatic postmenopausal osteoporosis, assessed by bone biopsy. A competitive protein binding assay was used, which included a chromatographic step. Accurate surveys of dietary or therapeutic vitamin D intake and light environment were obtained in each patient. Women with severe postmenopausal osteoporosis were found to have significantly (P less than 0.001) higher serum levels of 25-hydroxyvitamin D than age-matched normal women, the mean values being 27.5 ng/ml (+/- 13.6 SD) and 9.2 ng/ml (+/-5.7), respectively. The authors hypothesize that the reduction in 1,25-dihydroxyvitamin D, recently reported in postmenopausal osteoporotic women, might be responsible for the increased serum levels of 25-hydroxyvitamin D through an inadequate product inhibition of liver vitamin D 25-hydroxylase.

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Vitamin D

Cited by 15 publications

References 63 publications

Problems in the assessment of magnesium depletion in the rat byin vivo³¹P NMR

Problems in the assessment of magnesium depletion in the rat byin vivo³¹P NMR

Regulation of 25-Hydroxy-Vitamin D-1α-Hydroxylase in Chick Isolated Renal Tubules: Effects of Prostaglandin E2, Frusemide and Acetylsalicylic Acid

Serum levels of 25-hydroxyvitamin D in postmenopausal osteoporosis

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Vitamin D

Cited by 15 publications

References 63 publications

Problems in the assessment of magnesium depletion in the rat byin vivo31P NMR

Problems in the assessment of magnesium depletion in the rat byin vivo31P NMR

Regulation of 25-Hydroxy-Vitamin D-1α-Hydroxylase in Chick Isolated Renal Tubules: Effects of Prostaglandin E2, Frusemide and Acetylsalicylic Acid

Serum levels of 25-hydroxyvitamin D in postmenopausal osteoporosis

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Problems in the assessment of magnesium depletion in the rat byin vivo³¹P NMR

Problems in the assessment of magnesium depletion in the rat byin vivo³¹P NMR