24,25(OH)2D3 affects the calcemic effects of 1,25(OH)2D3 by mechanisms independent of intestinal calcium absorption

Rubinger, Dvora; Krause, Ilan; Alkoby-Gibbs, M.; Popovtzer, Mordecai M.

doi:10.1016/0169-6009(91)90127-l

Cited by 4 publications

(2 citation statements)

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“…20 Absorption of calcium from the gut is increased by 1 ,25(OH) 2 D 3, [21][22][23] whereas it has been shown that 24R,25(OH) 2 D 3 does not aVect this regulation of calcium uptake from the small intestine. 24 Both metabolites are implicated in the turnover of calcium in bone, with 1 ,25(OH) 2 D 3 considered more important in the control of osteoclasts, 25 26 and 24R,25(OH) 2 D 3 more eVective on the osteoblasts. 27 Dietary lead intake aVects the absorption of calcium from the gut 28 and interferes with bone formation.…”

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confidence: 99%

Measurement of vitamin D3 metabolites in smelter workers exposed to lead and cadmium.

Chalkley¹,

Richmond²,

Barltrop³

1998

Occup Environ Med

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Objectives-To investigate the eVects of lead and cadmium on the metabolic pathway of vitamin D 3 . Methods-Blood and urinary cadmium and urinary total proteins were measured in 59 smelter workers occupationally exposed to lead and cadmium. This study sought to investigate the eVect of exposure to the heavy metals lead and cadmium on the plasma concentrations of vitamin D 3 metabolites and to determine the eVects of dual exposure. The metabolic pathway of vitamin D 3 , cholecalciferol, involves the gut, liver, kidneys, and bones, all of which are aVected by these metals.1 2 The liver and kidneys are target organs for lead and cadmium, so that a potential biochemical eVect might be found in the vitamin D 3 pathway to explain the changes in bone metabolism found after exposure to lead or cadmium.3-6 Damage caused by cadmium to the renal tubules 7 8 was considered especially relevant to the formation of the more active dihydroxy metabolites, 24R, 25-dihydroxycholecalciferol (24R,25(OH) 2 D 3 ) and 1 , 25-dihydroxycholecalciferol, (1 ,25 (OH) 2 D 3 ).In the human, vitamin D 3 is obtained either from the diet 9 10 or is metabolised from 7-dehydrocholesterol by the epidermis in the presence of sunlight or ultraviolet light.

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confidence: 99%

Measurement of vitamin D3 metabolites in smelter workers exposed to lead and cadmium.

Chalkley¹,

Richmond²,

Barltrop³

1998

Occup Environ Med

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“…24,25(OH)2D3 alone did not affect plasma calcium. The blunting of the hypercalcemic effect of 1 ,25(OH)2D3 by 24,25(OH)2D3 was not explained by changes in urinary calcium (1) or by alterations in the intestinal absorption of calcium (2).…”

mentioning

confidence: 96%

The Influence of 24,25(OH)2D3 on the Calcemic Effect of 1,25(OH)2D in Rats with Chronic Renal Failure Is Parathyroid Hormone Dependent

Rubinger

Krause

et al. 1990

Experimental Biology and Medicine

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Previous studies from our laboratory have shown that 24,25(OH)2D3 attenuates the calcemic effect of 1,25(OH)2D3 in rats with reduced renal mass. This study was undertaken to clarify the role of parathyroid hormone in this response. Adult rats (n = 27) with reduced renal mass after parathyroidectomy with an initial plasma calcium of 3.7 +/- 0.1 mEq/liter were divided into four groups: (i) control rats and rats treated with (ii) 24,25(OH)2D3, (iii) 1,25(OH)2D3, and (iv) both 1,25 and 24,25(OH)2D3. After 4 days significant hypercalcemia was seen in PTX animals receiving 1,25(OH)2D3 alone or in combination with 24,25(OH)2D3. Plasma calcium in the combined therapy rats (7.42 +/- 0.22 mEq/liter) was significantly higher than in those treated with 1,25(OH)2D3 alone (6.68 +/- 0.22 mEq/liter, P less than 0.05). After 8 days, plasma calcium was higher in the rats treated with 1,25(OH)2D3 but was of same magnitude in those treated with 1,25(OH)2D3 alone or in combination with 24,25(OH)2D3. In contrast, in a subset of rats (n = 35) with reduced renal mass but intact parathyroid glands similarly treated with the vitamin D metabolites, a blunted calcemic response was seen after the combination of 1,25(OH)2D3 with 25,25(OH)2D3 administration alone. These results show that in rats with reduced renal mass, 24,25(OH)2D3 attenuates the calcemic effect of 1,25(OH)2D3 only in the presence of intact parathyroid glands. The different calcemic responses to 1,25 or combined 1,25 and 24,25(OH)2D3 in intact or parathyroidectomized rats with chronic renal insufficiency may result from different interaction between the vitamin D metabolites and the parathyroid hormone, presumably at the level of bone.

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2012

Pathology of the Hard Dental Tissues

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24,25(OH)2D3 affects the calcemic effects of 1,25(OH)2D3 by mechanisms independent of intestinal calcium absorption

Cited by 4 publications

References 10 publications

Measurement of vitamin D3 metabolites in smelter workers exposed to lead and cadmium.

Measurement of vitamin D3 metabolites in smelter workers exposed to lead and cadmium.

The Influence of 24,25(OH)2D3 on the Calcemic Effect of 1,25(OH)2D in Rats with Chronic Renal Failure Is Parathyroid Hormone Dependent

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