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1.
《Bone and mineral》1989,5(3):259-269
The pediatrician's interest in vitamin D metabolism stems from the once-endemic rachitic deformities induced by vitamin D deficiency; later, clinical research of inherited forms of rickets established further principles of vitamin D metabolism and action. Constantine Anast, as both clinician and researcher, maintained an enthusiastic interest in vitamin D metabolism. His investigative esprit fostered my interest, as a fellow in his laboratory, in the synthetic pathway of active vitamin D.The best known active metabolite of vitamin D, 1,25(OH)2D, is formed by 1βhydroxylation of 25(OH)D, the most abundant circulating form of the vitamin. This well-characterized biochemical conversion is the rate-limiting reaction in the synthesis of 1,25(OH)2D [1]. The classical homeostatic role of 1,25(OH)2D is predominantly that of a calcemie agent, an action largely resulting from the metabolite's stimulation of intestinal transport of calcium [2]. Intestinal phosphorus transport, to a lesser extent than calcium transport can be stimulated by 1,25(OH)2D [3]. Furthermore, skeletal [4] and perhaps renal activity [5] of 1,25(OH)2D can increase circulating concentrations of calcium. These in vivo effects of 1,25(OH)2D on mineral homeostasis raise the question of whether feedback control, via mineral regulation of 1,25(OH)2D production, exists, and the significant mechanisms involved. Here, I will briefly review evidence from earlier studies supporting the notion of calcium and phosphorus regulation of 1α-hydroxylase activity, and present data generated in collaboration with Dr Anast examining vitamin D metabolism in magnesium deficiency. 相似文献
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The essential role of vitamin D throughout the life of most mammals and birds as a mediator of calcium homeostasis is well established. In view of the complex endocrine system existent for the regulated metabolism of vitamin D3 to both 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] and 24R,25-dihydroxyvitamin D3 [24R,25-(OH)2D3] (both produced by the kidney), an intriguing problem is to elucidate whether only one or both of these dihydroxyvitamin D3 metabolites is required for the generation of all the biological responses mediated by the parent vitamin D3. In contrast to the accumulated knowledge concerning the short term actions of 1,25(OH)2-D3 on stimulating intestinal calcium absorption and bone calcium reabsorption, relatively little is known of the biological function of 24,25(OH)2D3. We report now the results of a nine month study in which chicks were raised on a vitamin D-deficient diet from hatching to sexual maturity and received as their sole source of “vitamin D” either 24,25(OH)2D3 or 1,25(OH)2D3 singly or in combination. Specifically we are describing the integrated operation of the vitamin D endocrine system as quantitated by the individual measurement in all birds of 22 variables related to “vitamin D status” and as evaluated by the statistical procedure of multivariate discriminant analysis. Twelve of these variables involved detailed analysis of the bone including quantitative histology and the other 10 variables reflect various manifestations of vitamin D action, e.g. serum Ca2+ and Pi levels, vitamin D-dependent calcium binding protein (CaBP) in the intestine and kidney, egg productivity etc. As evaluated by the multivariate analysis, it is clear that 24,25(OH)2D3 and 1,25(OH)2D3 are simultaneously required for normalization of calcium homeostasis. 相似文献
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The biologically active metabolite of vitamin D3, 1,25 (OH)2 D3, exerts important immunoregulatory effects in addition to being a central mediator of calcium/phosphate metabolism. Utilizing an interleukin 1 responsive murine T cell line and 125I-interleukin 1α, we show that 1,25 (OH)2 D3 (5,50 nM) enhanced 125I-interleukin 1α binding up to almost 2-fold over control. This 1,25 (OH)2 D3 effect occurred in a dose-dependent manner and was detectable after 24 h but not before 7 h of culture. Scatchard analysis of 125I-interleukin 1α binding data demonstrated that 1,25 (OH)2 D3 enhanced interleukin 1 receptor number without a significant change in affinity. The biologically less potent metabolite of vitamin D3, 25 (OH) D3, also augmented 125I-interleukin 1α binding but at steroid levels 2–3 log orders greater than 1,25 (OH)2 D3. This observation, combined with the presence of high-affinity 3H-1,25 (OH)2 D3 receptors (88 sites/cell, K = 0.45 nM) in cytosolic extracts, strongly suggests that the nuclear vitamin D receptor mediates this steroid's effect on interleukin 1 receptor expression. Based on the capacity of an anti-type 1 interleukin 1 receptor monoclonal antibody (35F5) to block 1,25 (OH)2 D3-enhanced 125I-interleukin 1α binding, we conclude that this steroid augments type 1 interleukin 1 receptor expression. When combined with interleukin 1, a cytokine that also impacts MD10 interleukin 1 receptor expression, 1,25 (OH)2 D3 enhanced interleukin 1 receptor expression. Northern blots hybridized with a 32P-type 1 interleukin 1 receptor cDNA probe show that 1,25 (OH)2 D3 enhanced type 1 interleukin 1 receptor steady state mRNA levels. Functionally, 1,25 (OH)2 D3 pretreatment augmented the MD10 proliferative response to suboptimal levels of interleukin 1 (< 100 fM interleukin 1α). These findings further support 1,25 (OH)2 D3's role as an immunoregulatory molecule and provides a possible mechanism by which this steroid could potentiate certain immune activities. 相似文献
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The mode of action of vitamin D3 (a seco steroid with a broken B ring) for calcium and phosphorus homeostasis is mediated at least in part through its metabolic transformation to 1, 25-dihydroxyvitamin D and 24, 25-dihydroxyvitamin D3. A vitamin D endocrine system produces in a carefully regulated fashion amounts of 1, 25(OH)2D3dictated by the calcium needs of the organism. 1, 25(OH)2D3 is known to induce the biosynthesis of a a calcium binding protein in the intestine and kidney via a mechanism similar to that of classic steroid hormones. Evidence for biological effects specifically generated by 24, 25(OH)2D3 D have also been obtained. Definite evidence for the further metabolism of these dihydroxylated metabolites exists; it probably occurs via side chain cleavage with the generation of several new molecules of unknown function. Evaluation of the unique structural aspects of these putative vitamin D metabolites suggests a second set of chemical and biological properties which could link these compounds structurally to the membrane-active polyene antibiotic filipin. These properties may rationalize some reported “rapid biological effects” pertaining to vitamin D and metabolites which hitherto have been difficult to explain in terms of classical steroid hormone theory. A key unresolved question relates to identification of the evolutionary pathways which resulted in the selection of vitamin D seco-steroids rather than classical (with intact rings) steroids for Ca and P homeostasis. 相似文献
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Seong Min Lee Erin M. Riley Mark B. Meyer Nancy A. Benkusky Lori A. Plum Hector F. DeLuca J. Wesley Pike 《The Journal of biological chemistry》2015,290(29):18199-18215
1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) plays an integral role in calcium homeostasis in higher organisms through its actions in the intestine, kidney, and skeleton. Interestingly, although several intestinal genes are known to play a contributory role in calcium homeostasis, the entire caste of key components remains to be identified. To examine this issue, Cyp27b1 null mice on either a normal or a high calcium/phosphate-containing rescue diet were treated with vehicle or 1,25(OH)2D3 and evaluated 6 h later. RNA samples from the duodena were then subjected to RNA sequence analysis, and the data were analyzed bioinformatically. 1,25(OH)2D3 altered expression of large collections of genes in animals under either dietary condition. 45 genes were found common to both 1,25(OH)2D3-treated groups and were composed of genes previously linked to intestinal calcium uptake, including S100g, Trpv6, Atp2b1, and Cldn2 as well as others. An additional distinct network of 56 genes was regulated exclusively by diet. We then conducted a ChIP sequence analysis of binding sites for the vitamin D receptor (VDR) across the proximal intestine in vitamin D-sufficient normal mice treated with vehicle or 1,25(OH)2D3. The residual VDR cistrome was composed of 4617 sites, which was increased almost 4-fold following hormone treatment. Interestingly, the majority of the genes regulated by 1,25(OH)2D3 in each diet group as well as those found in common in both groups contained frequent VDR sites that likely regulated their expression. This study revealed a global network of genes in the intestine that both represent direct targets of vitamin D action in mice and are involved in calcium absorption. 相似文献
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Moira Van Auken Denise Buckley Rahul Ray Michael F. Holick Daniel T. Baran 《Journal of cellular biochemistry》1996,63(3):302-310
The actions of the hormonal form of vitamin D, 1α,25-dihydroxyvitamin D3 [1α,25-(OH)2D3], are mediated by both genomic and nongenomic mechanisms. Several vitamin D synthetic analogs have been developed in order to identify and characterize the site(s) of action of 1α,25-(OH)2D3 in many cell types including osteoblastic cells. We have compared the effects of 1α,25-(OH)2D3 and a novel 1α,25-(OH)2D3 bromoester analog (1,25-(OH)2-BE) that covalently binds to vitamin D receptors. Rat osteosarcoma cells that possess (ROS 17/2.8) or lack (ROS 24/1) the classic intracellular vitamin D receptor were studied to investigate genomic and nongenomic actions. In ROS 17/2.8 cells plated at low density, the two vitamin D compounds (1 × 10−8 M) caused increased cell proliferation, as assessed by DNA synthesis and total cell counts. Northern blot analysis revealed that the mitogenic effect of both agents was accompanied by an increase in steady-state osteocalcin mRNA levels, but neither agent altered alkaline phosphatase mRNA levels in ROS 17/2.8 cells. ROS 17/2.8 cells responded to 1,25-(OH)2-BE but not the natural ligand with a significant increase in osteocalcin secretion after 72, 96, 120, and 144 hr of treatment. Treatment of ROS 17/2.8 cells with the bromoester analog also resulted in a significant decrease in alkaline phosphatase-specific activity. To compare the nongenomic effects of 1α,25-(OH)2D3 and 1,25-(OH)2-BE, intracellular calcium was measured in ROS 24/1 cells loaded with the fluorescent calcium indicator Quin 2. At 2 × 10−8 M, both 1α,25-(OH)2D3 and 1,25-(OH)2-BE increased intracellular calcium within 5 min. Both the genomic and nongenomic actions of 1,25-(OH)2-BE are similar to those of 1α,25-(OH)2D3, and since 1,25-(OH)2-BE has more potent effects on osteoblast function than the naturally occurring ligand due to more stable binding, this novel vitamin D analog may be useful in elucidating the structure and function of cellular vitamin D receptors. © 1996 Wiley-Liss, Inc. 相似文献
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J.L. Taft M. French J.A. Danks R.G. Larkins 《Biochemical and biophysical research communications》1984,121(1):355-363
In contrast to dibuturyl cyclic AMP, the methylxanthine phosphodiesterase inhibitors theophylline and caffeine were found to inhibit the conversion of 25 hydroxyvitamin D3 to 1,25 dihydroxyvitamin D3 in isolated renal tubules from vitamin D deficient chicks. This inhibition occurred at concentrations of methylxanthines which were shown to increase renal tubule cyclic AMP levels. No effect of theophylline or caffeine on 25 hydroxyvitamin D3 metabolism in isolated chick renal mitochondria was detected. Because of a demonstrated inhibitory action of calcium (10 and 20 μmol/l) on renal mitochondrial conversion of 25 hydroxyvitamin D3 to 1,25 dihydroxyvitamin D3, the effect of theophylline and dibutyryl cyclic AMP on cellular calcium-45 efflux and total renal tubule calcium content was estimated. Theophylline 10 mmol/l was found to inhibit renal tubular calcium efflux and to increase total cellular calcium content, while dibutyryl cyclic AMP 1 mmol/l had the reverse effect on both parameters. Divergent actions of the methylxanthines and dibutyryl cyclic AMP on the formation of 1,25 dihydroxyvitamin D3 and renal tubule calcium efflux and content support the hypothesis that intracellular calcium is an important regulator of renal vitamin D metabolism. The results indicate that observed actions of methylxanthines cannot always be ascribed to cyclic AMP accumulation. 相似文献
11.
The active form of vitamin D, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), can suppress disease in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Calcium appears to be a critical component of 1,25(OH)2D3-mediated suppression of EAE, as complete disease prevention only occurs with a concomitant increase in serum calcium levels. Calcitonin (CT) is a peptide hormone released in response to acute increases in serum calcium, which led us to explore its importance in 1,25(OH)2D3-mediated suppression of EAE. Previously, we discovered that co-administration of pharmacological doses of CT enhanced the suppressive effect of 1,25(OH)2D3 on EAE, suggesting CT may play a role in 1,25(OH)2D3-mediated suppression of EAE. To determine the importance of CT in EAE we have utilized a mouse strain in which the gene encoding CT and its alternative splice product, calcitonin gene related peptide-α (CGRP), have been deleted. Deletion of the CT/CGRP gene had no effect on EAE progression. Furthermore, treatment with 1,25(OH)2D3 suppressed EAE in CT/CGRP knock-out mice equal to that in wild type mice. Therefore, we conclude that CT is not necessary for 1,25(OH)2D3-mediated suppression of EAE. 相似文献
12.
When 1,25(OH)2-vitamin D3 was administered to vitamin D-deficient chicks, within two hours the parathyroid glands were observed to accumulate this steroid to a concentration four times that present in the blood and equivalent to levels observed in the target intestine. Similarly, when 25-(OH)-vitamin D3 was administered, the parathyroid glands had 2.4 times the concentration of the metabolite, 1,25-(OH)2-vitamin D3 as that seen in the blood and 60% of that found in the intestine. These results are consistent with the concept that the hormonally active form of vitamin D, 1,25-(OH)2-vitamin D3, may interact with the parathyroid glands to effect changes in parathyroid hormone secretion. 相似文献
13.
K. van der Meijden N. Bravenboer N.F. Dirks A.C. Heijboer M. den Heijer G.M.J. de Wit C. Offringa P. Lips R.T. Jaspers 《Journal of cellular physiology》2016,231(11):2517-2528
An adequate vitamin D status is essential to optimize muscle strength. However, whether vitamin D directly reduces muscle fiber atrophy or stimulates muscle fiber hypertrophy remains subject of debate. A mechanism that may affect the role of vitamin D in the regulation of muscle fiber size is the local conversion of 25(OH)D to 1,25(OH)2D by 1α‐hydroxylase. Therefore, we investigated in a murine C2C12 myoblast culture whether both 1,25(OH)2D3 and 25(OH)D3 affect myoblast proliferation, differentiation, and myotube size and whether these cells are able to metabolize 25(OH)D3 and 1,25(OH)2D3. We show that myoblasts not only responded to 1,25(OH)2D3, but also to the precursor 25(OH)D3 by increasing their VDR mRNA expression and reducing their proliferation. In differentiating myoblasts and myotubes 1,25(OH)2D3 as well as 25(OH)D3 stimulated VDR mRNA expression and in myotubes 1,25(OH)2D3 also stimulated MHC mRNA expression. However, this occurred without notable effects on myotube size. Moreover, no effects on the Akt/mTOR signaling pathway as well as MyoD and myogenin mRNA levels were observed. Interestingly, both myoblasts and myotubes expressed CYP27B1 and CYP24 mRNA which are required for vitamin D3 metabolism. Although 1α‐hydroxylase activity could not be shown in myotubes, after treatment with 1,25(OH)2D3 or 25(OH)D3 myotubes showed strongly elevated CYP24 mRNA levels compared to untreated cells. Moreover, myotubes were able to convert 25(OH)D3 to 24R,25(OH)2D3 which may play a role in myoblast proliferation and differentiation. These data suggest that skeletal muscle is not only a direct target for vitamin D3 metabolites, but is also able to metabolize 25(OH)D3 and 1,25(OH)2D3. J. Cell. Physiol. 231: 2517–2528, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc. 相似文献
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Ahmed M. Kamr Katarzyna A. Dembek Stephen M. Reed Nathan M. Slovis Ahmed A. Zaghawa Thomas J. Rosol Ramiro E. Toribio 《PloS one》2015,10(6)
Background
Hypocalcemia is a frequent abnormality that has been associated with disease severity and outcome in hospitalized foals. However, the pathogenesis of equine neonatal hypocalcemia is poorly understood. Hypovitaminosis D in critically ill people has been linked to hypocalcemia and mortality; however, information on vitamin D metabolites and their association with clinical findings and outcome in critically ill foals is lacking. The goal of this study was to determine the prevalence of vitamin D deficiency (hypovitaminosis D) and its association with serum calcium, phosphorus, and parathyroid hormone (PTH) concentrations, disease severity, and mortality in hospitalized newborn foals.Methods and Results
One hundred newborn foals ≤72 hours old divided into hospitalized (n = 83; 59 septic, 24 sick non-septic [SNS]) and healthy (n = 17) groups were included. Blood samples were collected on admission to measure serum 25-hydroxyvitamin D3 [25(OH)D3], 1,25-dihydroxyvitamin D3 [1,25(OH) 2D3], and PTH concentrations. Data were analyzed by nonparametric methods and univariate logistic regression. The prevalence of hypovitaminosis D [defined as 25(OH)D3 <9.51 ng/mL] was 63% for hospitalized, 64% for septic, and 63% for SNS foals. Serum 25(OH)D3 and 1,25(OH) 2D3 concentrations were significantly lower in septic and SNS compared to healthy foals (P<0.0001; P = 0.037). Septic foals had significantly lower calcium and higher phosphorus and PTH concentrations than healthy and SNS foals (P<0.05). In hospitalized and septic foals, low 1,25(OH)2D3 concentrations were associated with increased PTH but not with calcium or phosphorus concentrations. Septic foals with 25(OH)D3 <9.51 ng/mL and 1,25(OH) 2D3 <7.09 pmol/L were more likely to die (OR=3.62; 95% CI = 1.1-12.40; OR = 5.41; 95% CI = 1.19-24.52, respectively).Conclusions
Low 25(OH)D3 and 1,25(OH)2D3 concentrations are associated with disease severity and mortality in hospitalized foals. Vitamin D deficiency may contribute to a pro-inflammatory state in equine perinatal diseases. Hypocalcemia and hyperphosphatemia together with decreased 1,25(OH)2D3 but increased PTH concentrations in septic foals indicates that PTH resistance may be associated with the development of these abnormalities. 相似文献16.
We investigated the occurrence of rickets in adolescent tamarins (Saguinus imperator) residing at the Los Angeles Zoo. Compared to tamarins in the same colony without clinical evidence of bone disease (N = 6), rachitic platyrrhines (N = 3) had a decrease in their serum calcium concentration (P < .05). The affected tamarins also had lower serum 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) levels than did nonaffected colony mates, but 2–10-fold higher concentrations than in Old World primates of a comparable developmental stage. New World primates in many different genera are known to exhibit target organ resistance to the active vitamin D3 metabolite, 1,25-(OH)2D3, compensated by maintenance of high circulating concentrations of 1,25-(OH)2D3. The relatively low serum 1,25-(OH)2D3 concentration in rachitic tamarins and ultraviolet B radiation deficient environment of these primates suggested that bone disease may be linked to a deficiency in substrate for 1,25-(OH)2D3, 25 hydroxyvtamin D3 (25-OHD3). Chronic exposure of platyrrhines in three different vitamin D resistant genera to an artificial UVB source resulted in 1) a significant increase in the mean serum 25-OHD3 (P < .001) and 1,25-(OH)2D3 (P < .02) level over that encountered in platyrrhines not exposed to UVB; and 2) prevention of rachitic bone disease in irradiated individuals. These data further show that the serum 25-OHD3 and 1,25-OH2D3 levels are positively correlated in vitamin D-resistant platyrrhines (r = 0.64; P= .0014) and suggest that a compromise in cutaneous vitamin D3 production by means of UVB deprivation may limit necessary 1,25-(OH)2D3 production. © 1992 Wiley-Liss, Inc. 相似文献
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A scientific explanation for the beneficial role of vitamin D supplementation in the lowering of glycemia in diabetes remains to be determined. This study examined the biochemical mechanism by which vitamin D supplementation regulates glucose metabolism in diabetes. 3T3L1 adipocytes were treated with high glucose (HG, 25 mm) in the presence or absence of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (25, 50 nm), the active form of vitamin D. 1,25(OH)2D3 treatment caused significant up-regulation of GLUT4 total protein expression and its translocation to cell surface, and an increase in glucose uptake as well as glucose utilization in HG-treated cells. 1,25(OH)2D3 also caused cystathionine-γ-lyase (CSE) activation and H2S formation in HG-treated adipocytes. The effect of 1,25(OH)2D3 on GLUT4 translocation, glucose utilization, and H2S formation was prevented by propargylglycine, an inhibitor of CSE that catalyzes H2S formation. Studies using antisense CSE also demonstrated the inhibition of GLUT4 translocation as well as glucose uptake and utilization in 1,25(OH)2D3-supplemented CSE-siRNA-transfected adipocytes compared with controls. 1,25(OH)2D3 treatment along with insulin enhanced GLUT4 translocation and glucose utilization compared with either insulin or 1,25(OH)2D3 alone in HG-treated adipocytes. 1,25(OH)2D3 supplementation also inhibited monocyte chemoattractant protein-1 and stimulated adiponectin secretion in HG-treated adipocytes, and this positive effect was prevented in propargylglycine-treated or CSE-knockdown adipocytes. This is the first report to demonstrate that 1,25(OH)2D3 up-regulates GLUT4 translocation and glucose utilization and decreases inflammatory markers, which is mediated by CSE activation and H2S formation in adipocytes. This study provides evidence for a novel molecular mechanism by which 1,25(OH)2D3 can up-regulate the GLUT4 translocation essential for maintenance of glucose metabolism. 相似文献
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Anna E. Goodroe Casey Fitz Michael L. Power Ricki J. Colman Saverio Capuano III Toni E. Ziegler 《American journal of primatology》2020,82(6):e23131
Vitamin D3 (cholecalciferol) is endogenously produced in the skin of primates when exposed to the appropriate wavelengths of ultraviolet light (UV-B). Common marmosets (Callithrix jacchus) maintained indoors require dietary provision of vitamin D3 due to lack of sunlight exposure. The minimum dietary vitamin D3 requirement and the maximum amount of vitamin D3 that can be metabolized by marmosets is unknown. Observations of metabolic bone disease and gastrointestinal malabsorption have led to wide variation in dietary vitamin D3 provision amongst research institutions, with resulting variation in circulating 25-hydroxyvitamin D3 (25(OH)D3), the accepted marker for vitamin D sufficiency/deficiency. Multiple studies have reported serum 25(OH)D3 in captive marmosets, but 25(OH)D3 is not the final product of vitamin D3 metabolism. In addition to serum 25(OH)D3, we measured the most physiologically active metabolite, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and the less well understood metabolite, 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) to characterize the marmoset's ability to metabolize dietary vitamin D3. We present vitamin D3 metabolite and related serum chemistry value colony reference ranges in marmosets provided diets with 26,367 (Colony A, N = 113) or 8,888 (Colony B, N = 52) international units (IU) of dietary vitamin D3 per kilogram of dry matter. Colony A marmosets had higher serum 25(OH)D3 (426 ng/ml [SD 200] vs. 215 ng/ml [SD 113]) and 24,25(OH)2D3 (53 ng/ml [SD 35] vs. 7 ng/ml [SD 5]). There was no difference in serum 1,25(OH)2D3 between the colonies. Serum 1,25(OH)2D3 increased and 25(OH)D3 decreased with age, but the effect was weak. Marmosets tightly regulate metabolism of dietary vitamin D3 into the active metabolite 1,25(OH)2D3; excess 25(OH)D3 is metabolized into 24,25(OH)2D3. This ability explains the tolerance of high levels of dietary vitamin D3 by marmosets, however, our data suggest that these high dietary levels are not required. 相似文献
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R L Johnson W H Okamura A W Norman 《Biochemical and biophysical research communications》1975,67(2):797-802
24-Nor-25-hydroxyvitamin D3, an analog of 25-hydroxyvitamin D3, has been chemically synthesized in six steps. This steroid was tested in chicks, , for its ability to generate the classic vitamin D mediated responses of stimulation of intestinal calcium transport and bone calcium mobilization. Although the 24-nor-25-OH-vitamin D3 itself exhibited no biological activity in these assays, the analog was found to inhibit the normal responses produced by a physiological dose of vitamin D3. These results suggest that 24-nor-25-OH-vitamin D3 may satisfy certain requirements expected of a calciferol “anti-vitamin.” 相似文献