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1.
Kidney tubules obtained from chicks fed a high-calcium low-phosphorus diet retained 25-hydroxyvitamin D3-1-hydroxylase activity after a 10 h incubation in serum-free minimum essential medium. Inclusion of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) in the medium prompted a suppression of 25-hydroxyvitamin D3-1-hydroxylase and the induction of 25-hydroxyvitamin D3-24-hydroxylase activities. The enzyme switch-over response could be prompted by 1.6 × 10?7 M 1,25-dihydroxyvitamin D3 and occurred within 6 h following treatment. Medium calcium appeared to augment the metabolite's switch-over action. 相似文献
2.
25,26-dihydroxyvitamin D3 is not a major intermediate in 25-hydroxyvitamin D3-26,23-lactone formation 总被引:1,自引:0,他引:1
Structural similarities between 25S,26-dihydroxyvitamin D3 and 25-hydroxyvitamin D3-26,23-lactone and their concomitant multifold increase in the plasma of animals treated with pharmacological doses of vitamin D3 suggest a precursor-product relationship. However, a single dose of 25S,26-[3H]dihydroxyvitamin D3 given to rats treated chronically with pharmacological amounts of vitamin D3 did not result in detectable plasma 25-[3H]hydroxyvitamin D3-26,23-lactone. Multiple doses of synthetic 25S,26-dihydroxyvitamin D3 given to vitamin D3-deficient rats treated chronically with pharmacological amounts of vitamin D2 also did not result in detectable plasma 25-hydroxyvitamin D3-26,23-lactone. Furthermore, homogenates prepared from vitamin d-deficient chickens, dosed with 1,25-dihydroxyvitamin D3, converted 25-[3H]hydroxyvitamin D3 to 25-[3H]hydroxyvitamin D3-26,23-lactone. But these same homogenates did not convert 25S,26-[3H]dihydroxyvitamin D3 to 25-[3H]hydroxyvitamin D3-26,23-lactone. These data indicate that 25,26-dihydroxyvitamin D3 is not an intermediate in 25-hydroxyvitamin D326, 23-lactone formation. 相似文献
3.
L. Castillo Y. Tanaka H.F. DeLuca M.L. Sunde 《Archives of biochemistry and biophysics》1977,179(1):211-217
Homogenates of kidney from laying Japanese quail incubated in vitro with 25-hydroxy-[26,27-3H] vitamin D3 produce more 1,25-dihydroxy-[26,27-3H]vitamin D3 than do homogenates of kidney from mature nonlaying females or males maintained on the same diet and under identical conditions. Instead, the homogenates from male quail or nonlaying female quail convert 25-hydroxyvitamin D3 to 24,25-dihydroxyvitamin D3. The administration of 5 mg of estradiol to mature male quail 24 h prior to sacrifice suppressed the 25-hydroxyvitamin D3-24-hydroxylase and markedly stimulated 25-hydroxyvitamin D3-1-hydroxylase. The administration of estradiol to male quail caused hypercalcemia, which responded more slowly than did the 1-hydroxylase. As little as 0.1 mg of estradiol/quail was found effective in stimulating the 1-hydroxylase and suppressing the 24-hydroxylase. Other hormones such as follicle stimulating hormone (FSH), cortisone, testosterone, and progesterone, even at high dose levels, produced little or no change in the 25-hydroxyvitamin D3-1-hydroxylase. Testosterone did, however, suppress the 25-hydroxyvitamin D3-24-hydroxylase. The stimulation of the 25-hydroxyvitamin D3-1-hydroxylase by parathyroid hormone was of a smaller magnitude than that of the estradiol, and the effects of the two hormones were additive, suggesting that they function by a different mechanism. 相似文献
4.
Two new sidechain-modified analogs of vitamin D3, 25-azavitamin D3 and 25-fluorovitamin D3, were prepared; both compounds were found to inhibit the in vivo 25-hydroxylation of vitamin D3 in the rat. 25-Azavitamin D3 was chemically synthesized from a degradation product of stigmasterol by a six-step process. The desired carbon skeleton was efficiently assembled by alkylation of a suitably protected C-20 bromomethylpregnane with the enolate of N,N-dimethylacetamide (70%). The completion of the synthesis utilized the known photochemistry of steroidal 5,7-dienes to prepare the vitamin D triene system. In contrast, 25-fluorovitamin D3 was prepared by direct vitamin modification. 25-Hydroxyvitamin D3 3-acetate was fluorinated with diethylaminosulfur trifluoride to give 25-fluorovitamin D3 3-acetate (59%); saponification provided the desired analog. When vitamin D-deficient rats on a low calcium diet were dosed with [3-3H]vitamin D3 (0.05 μg), 10% of the dose was found in serum as 25-hydroxyvitamin D3 4 hr after administration. If 25-azavitamin D3 (50 or 200 μg) was given 2 hr before the radiolabeled vitamin D3, however, serum 25-hydroxyvitamin D3 concentration was markedly reduced. 25-Fluorovitamin D3 caused similar reduction when administered at much lower doses. 相似文献
5.
Yan-Ru Lou Ferdinand Molnár Mikael Peräkylä Shengjun Qiao Allan V. Kalueff René St-Arnaud Carsten Carlberg Pentti Tuohimaa 《The Journal of steroid biochemistry and molecular biology》2010,118(3):162-170
25-Hydroxyvitamin D3 1α-hydroxylase encoded by CYP27B1 converts 25-hydroxyvitamin D3 into 1α,25-dihydroxyvitamin D3, a vitamin D receptor ligand. 25-Hydroxyvitamin D3 has been regarded as a prohormone. Using Cyp27b1 knockout cells and a 1α-hydroxylase-specific inhibitor we provide in four cellular systems, primary mouse kidney, skin, prostate cells and human MCF-7 breast cancer cells, evidence that 25-hydroxyvitamin D3 has direct gene regulatory properties. The high expression of megalin, involved in 25-hydroxyvitamin D3 internalisation, in Cyp27b1?/? cells explains their higher sensitivity to 25-hydroxyvitamin D3. 25-Hydroxyvitamin D3 action depends on the vitamin D receptor signalling supported by the unresponsiveness of the vitamin D receptor knockout cells. Molecular dynamics simulations show the identical binding mode for both 25-hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3 with the larger volume of the ligand-binding pocket for 25-hydroxyvitamin D3. Furthermore, we demonstrate direct anti-proliferative effects of 25-hydroxyvitamin D3 in human LNCaP prostate cancer cells. The synergistic effect of 25-hydroxyvitamin D3 with 1α,25-dihydroxyvitamin D3 in Cyp27b1?/? cells further demonstrates the agonistic action of 25-hydroxyvitamin D3 and suggests that a synergism between 25-hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3 might be physiologically important. In conclusion, 25-hydroxyvitamin D3 is an agonistic vitamin D receptor ligand with gene regulatory and anti-proliferative properties. 相似文献
6.
Helen L. Henry 《Biochemical and biophysical research communications》1977,74(2):768-774
The primary culture of kidney cells from vitamin D deficient chicks is described. After four days in culture the cells reach confluency and retain their ability to metabolize 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3. Addition of one unit of bovine parathyroid hormone to the culture medium for 48 hours prior to assay had no effect on the cells' ability to produce 1,25-dihydroxy vitamin D3, whereas after 24 hours in the presence of 5×10?8 1,25-dihydroxyvitamin D3 the cells produced not this metabolite, but 24,25-dihydroxyvitamin D3. This cell culture system will allow the investigation of the regulation of renal 25-hydroxyvitamin D3 metabolism under controlled conditions. 相似文献
7.
Y Tanaka H F DeLuca A Akaiwa M Morisaki N Ikekawa 《Archives of biochemistry and biophysics》1976,177(2):615-621
An epimeric mixture of 24-hydroxy-[24-3H]vitamin D3 was synthesized by the reduction of 24-ketovitamin D3 by sodium borotritide. The epimeric mixture was converted to the trimethylsilylether derivatives and subjected to high-pressure liquid chromatography using silica gel columns to separate the 24-hydroxy-[24-3H]vitamin D3 isomers. The 24R-hydroxy-[24-3H] vitamin D3 induced calcification in rachitic rats while the 24S-hydroxy-[24-3H] vitamin D3 had little or no such activity. As both isomers of 24-hydroxy-vitamin D3 are metabolized to 24,25-dihydroxyvitamin D3, it appears that the 24-hydroxyvitamin D3-25-hydroxylase does not discriminate between the isomers. Only the R-isomer of 24-hydroxyvitamin D3 is metabolized to 1,24-dihydroxyvitamin D3, although only trace amounts of this compound were found 2 days after the administration of 24-hydroxyvitamin D3. The striking difference in the metabolism of the isomers is the high selectivity of the 1-hydroxylase for R-isomer. It is suggested that the high specificity of biological activity for the R-isomer of 24-hydroxyvitamin D3 is because of the specificity of the 1-hydroxylation of 24,25-dihydroxyvitamin D3 for the R configuration. 相似文献
8.
Seiichi Ishizuka Sachio Ishimoto Anthony W. Norman 《Archives of biochemistry and biophysics》1982,217(1):264-272
Kidney homogenates from vitamin D3-supplemented chicks incubated with 25-hydroxyvitamin D3 [25(OH)D3] produce significant quantities of a new, unknown vitamin D metabolite. This metabolite was isolated in pure form from such incubation mixtures by using Sephadex LH-20 column chromatography followed by high-pressure liquid chromatography. This metabolite has been identified as 23,25,26-trihydroxyvitamin D3 [23,25,26(OH)3D3] by loss of radioactivity from 25-hydroxy[23,24-3H]vitamin D3 and 25-hydroxy-[26,27-methyl-3H]vitamin D3, ultraviolet absorption spectrophotometry, mass spectrometry, and periodate cleavage oxidation followed by mass spectrometry. This same metabolite was also isolated from the serum of rats given large doses of vitamin D3, and structurally characterized as 23,25,26-trihydroxyvitamin D3. As yet, the stereochemistry at the C-23 and C-25 positions of the natural product remains unknown. A comparison of responses to a single dose level (500 ng) of 23,25,26(OH)3D3 or 25(OH)D3 over 96 h in vitamin D-deficient rats indicated that the new metabolite had no capability to mediate bone calcium mobilization and that it was only weakly active in stimulating intestinal calcium transport. 相似文献
9.
J L Napoli M A Fivizzani A J Hamstra H K Schnoes H F DeLuca 《Analytical biochemistry》1979,96(2):481-488
A synthesis of radiochemically pure 25-hydroxy[26,27-3H]vitamin D3 with a specific activity of 160 Ci/mmol is reported. The structure and biological activity of the radiolabeled compound was verified by comigration on high-pressure liquid chromatography with synthetic 25-hydroxyvitamin D3 to constant specific activity, and by conversion in vitro to 1α,25-dihydroxy[26,27-3H]vitamin D3 with the chick kidney 1α-hydroxylase. 相似文献
10.
Y. Tanaka J.K. Wichmann H.F. De Luca Y. Kobayashi N. Ikekawa 《Archives of biochemistry and biophysics》1983,225(2):649-655
To evaluate possible functional roles for 24,25-dihydroxyvitamin D3, 24,24-difluoro-25-hydroxyvitamin D3 has been synthesized and shown to be equally as active as 25-hydroxyvitamin D3 in all known functions of vitamin D. The use of the difluoro compound for this purpose is based on the assumption that the C-F bonds are stable in vivo and that the fluorine atom does not act as hydroxyl in biological systems. No 24,25-dihydroxyvitamin D3 was detected in the serum obtained from vitamin D-deficient rats that had been given 24,24-difluoro-25-hydroxyvitamin D3, while large amounts were found when 25-hydroxyvitamin D3 was given. Incubation of the 24,24-difluoro compound with kidney homogenate prepared from vitamin D-replete chickens failed to produce 24,25-dihydroxyvitamin D3, while the same preparations produced large amounts of 24,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3. Kidney homogenate prepared from vitamin D-deficient chickens produced 24,24-difluoro-1,25-dihydroxyvitamin D3 from 24,24-difluoro-25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3. In binding to the plasma transport protein for vitamin D compounds, 24,24-difluoro-25-hydroxyvitamin D3 is less active than 25-hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D3. In binding to the chick intestinal cytosol receptor, 24,24-difluoro-25-hydroxyvitamin D3 is more active than 25-hydroxyvitamin D3 which is itself more active than 24R,25-dihydroxyvitamin D3. The 24,24-difluoro-1,25-dihydroxyvitamin D3 is equal to 1,25-dihydroxyvitamin D3, and both are 10 times more active than 1,24R,25-trihydroxyvitamin D3 in this system. These results provide strong evidence that the C-24 carbon of 24,24-difluoro-25-hydroxyvitamin D3 cannot be hydroxylated in vivo, and, further, the 24-F substitution acts similar to H and not to OH in discriminating binding systems for vitamin D compounds. 相似文献
11.
Specific binding proteins for 1,25-dihydroxyvitamin D3 were identified in bovine mammary tissue obtained from lactating and non-lactating mammary glands by sucrose density gradient centrifugation. The macromolecules had characteristic sedimentation coefficients of 3.5-3.7 S. The interaction of l,25-dihydroxy[3H]vitamin D3 with the macromolecule of the mammary gland cytosol occurred at low concentrations, was saturable, and was a high affinity interaction (Kd = 4.2 × 10?10M at 25 °C). Binding was reversed by excess unlabeled 1,25-dihydroxyvitamin D3, was destroyed by heat and/or incubation with trypsin. It is thus inferred that this macromolecule is protein as it is not destroyed by ribonuclease or deoxyribonuclease. 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and vitamin D3 did not effectively compete with 1,25-dihydroxyvitamin D3 for binding to cytosol of mammary tissue at near physiological concentrations of these analogs, thus demonstrating the specificity of the binding protein for 1,25-dihydroxyvitamin D3. In vitro subcellular distribution of 1,25-dihydroxy[3H]vitamin D3 demonstrated a time- and temperature-dependent movement of the hormone from the cytoplasm to the nucleus. By 90 min at 25 °C 72% of the 1,25-dihydroxy[3H]vitamin D3 was associated with the nucleus. In addition a 5–6 S macromolecule which binds 25-hydroxy[3H]vitamin D3 was demonstrated in mammary tissue. Finally, it is possible that the receptor-hormone complex present in mammary tissue may function in a manner analogous to intestinal tissue, resulting in the control of calcium transport by 1,25-dihydroxyvitamin D3 in this tissue. 相似文献
12.
Anke Kleiner-Bossaller Hector F. Deluca 《Biochimica et Biophysica Acta (BBA)/General Subjects》1974,338(2):489-495
Incubation of [26,27-3H2]-25-hydroxyvitamin D3 with kidney homogenates from rats fed a high (3%) calcium vitamin D-supplemented diet results in the production of a more polar metabolite which cochromatographs with 1,24,25-trihydroxyvitamin D3. On the other hand, incubation with kidney homogenates from vitamin D-deficient or calcium-deficient rats did not produce the polar metabolite. Mitochondria but not microsomes carry out the reaction and evidence has been produced to demonstrate that the 1,24,25-trihydroxyvitamin D3 can be produced in vivo from either 1,25-dihydroxyvitamin D3 as previously reported. 相似文献
13.
Xavier Khawaja Non Evans Yvonne Reilly Christine Ennis Michael C. W. Minchin 《Journal of neurochemistry》1995,64(6):2716-2726
Abstract: The specific binding of [3H]WAY-100635 {N-[2-[4-(2-[O-methyl-3H]methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane carboxamide trihydrochloride} to rat hippocampal membrane preparations was time, temperature, and tissue concentration dependent. The rates of [3H]WAY-100635 association (k+1 = 0.069 ± 0.015 nM?1 min?1) and dissociation (k?1 = 0.023 ± 0.001 min?1) followed monoexponential kinetics. Saturation binding isotherms of [3H]WAY-100635 exhibited a single class of recognition site with an affinity of 0.37 ± 0.051 nM and a maximal binding capacity (Bmax) of 312 ± 12 fmol/mg of protein. The maximal number of binding sites labelled by [3H]WAY-100635 was ~36% higher compared with that of 8-hydroxy-2-(di-n-[3H]-propylamino)tetralin ([3H]8-OH-DPAT). The binding affinity of [3H]WAY-100635 was significantly lowered by the divalent cations CaCl2 (2.5-fold; p < 0.02) and MnCl2 (3.6-fold; p < 0.05), with no effect on Bmax. Guanyl nucleotides failed to influence the KD and Bmax parameters of [3H]WAY-100635 binding to 5-HT1A receptors. The pharmacological binding profile of [3H]WAY-100635 was closely correlated with that of [3H]8-OH-DPAT, which is consistent with the labelling of 5-hydroxytryptamine1A (5-HT1A) sites in rat hippocampus. [3H]WAY-100635 competition curves with 5-HT1A agonists and partial agonists were best resolved into high- and low-affinity binding components, whereas antagonists were best described by a one-site binding model. In the presence of 50 µM guanosine 5′-O-(3-thiotriphosphate) (GTPγS), competition curves for the antagonists remained unaltered, whereas the agonist and partial agonist curves were shifted to the right, reflecting an influence of G protein coupling on agonist versus antagonist binding to the 5-HT1A receptor. However, a residual (16 ± 2%) high-affinity agonist binding component was still apparent in the presence of GTPγS, indicating the existence of GTP-insensitive sites. 相似文献
14.
Erik H. F. Wong Douglas W. Bonhaus Irene Wu Eric Stefanich Richard M. Eglen 《Journal of neurochemistry》1993,60(3):921-930
Abstract: RS-42358–197{(S)-N-(1-azabicyclo[2.2.2]oct-3-yl)-2,4,5,6-tetrahydro-1H-benzo[de]isoquinolin-1-one hydrochloride} displaced the prototypic 5-hydroxytryptamine3 (5-HT3) receptor ligand [3H]quipazine in rat cerebral cortical membranes with an affinity (pKi) of 9.8 ± 0.1, while having weak affinity (pKi < 6.0) in 23 other receptor binding assays. [3H]RS-42358–197 was then utilized to label 5-HT3 receptors in a variety of tissues. [3H]RS-42358–197 labelled high-affinity and saturable binding sites in membranes from rat cortex, NG108–15 cells, and rabbit ileal myenteric plexus with affinities (KD) of 0.12 ± 0.01, 0.20 ± 0.01, and 0.10 ± 0.01 nM and densities (Bmax) of 16.0 ± 2.0, 660 ± 74, and 88 ± 12 fmol/mg of protein, respectively. The density of sites labelled in each of these tissues with [3H]RS-42358–197 was similar to that labelled with [3H]GR 65630, but was significantly less than that found with [3H]-quipazine. The binding of [3H]RS-42358–197 had a pharmacological profile similar to that of [3H]quipazine, as indicated by the rank order of displacement potencies: RS-42358–197 > (S)-zacopride > tropisetron > (R)-zacopride > ondansetron > MDL72222 > 5-HT. However, differences in 5-HT3 receptors of different tissues and species were detected on the basis of statistically significant differences in the affinities of phenylbiguanide, and 1-(m-chlorophenyl)biguanide when displacing [3H]RS-42358-197 binding. [3H]RS-42358–197 also labelled a population (Bmax= 91 ± 17 fmol/mg of protein) of binding sites in guinea pig myenteric plexus membranes, with lower affinity (KD= 1.6 ± 0.3 nM) than those in the other preparations. Moreover, the rank order of displacement potencies of 15 5-HT3 receptor ligands in guinea pig ileum was found not to be identical to that in other tissues. Binding studies carried out with [3H]RS-42358–197 have detected differences in 5-HT3 receptor binding sites in tissues of different species and further underscore the unique nature of the guinea pig 5-HT3 receptor. 相似文献
15.
Carlos Gregorio Silvina Eduardo Luis C. Rodrigues María A. Regueira Ramn Fraga Ricardo Riveiros Miguel Maestro Antonio Mourio 《The Journal of steroid biochemistry and molecular biology》2007,103(3-5):227
Hapten derivatives of 25-hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3 were synthesized using the Wittig–Horner approach. Both haptens bearing a carboxylic group at the side chain that can be linked to a protein for raising antibodies of potential utility for the determination of 25-hydroxyvitamin D3, 1α,25-dihydroxyvitamin D3 and 1α-hydroxylated vitamin D3 analogues. 相似文献
16.
《Endocrine practice》2012,18(3):399-402
ObjectiveTo examine the effect of 50 000 IU-vitamin D2 supplementation in a clinical setting on serum total 25-hydroxyvitamin D (25[OH]D), 25-hydroxyvitamin D2 (25[OH]D2), and 25-hydroxyvitamin D3 (25[OH]D3).MethodsThis retrospective cohort study was performed in an urban tertiary referral hospital in Boston, Massachusetts. Patients who had been prescribed 50 000 IU vitamin D2 repletion and maintenance programs were identified through a search of our electronic medical record. Baseline and follow-up total serum 25(OH)D, 25(OH)D2, and 25(OH)D3 levels were compared.ResultsWe examined the medical records of 48 patients who had been prescribed 50 000 IU vitamin D2 in our clinic. Mean ± standard deviation baseline total 25(OH) D was 31.0 ± 10.6 ng/mL and rose to 48.3 ± 13.4 ng/mL after treatment (P <.001). 25(OH)D2 increased from 4.2 ± 4.3 ng/mL to 34.6 ± 12.3 ng/mL after treatment (P <.001), for an average of 158 days (range, 35-735 days). Serum 25(OH)D3 decreased from 26.8 ± 10.8 ng/mL to 13.7 ± 7.9 ng/mL (P <.001).ConclusionsFifty thousand IU vitamin D2 repletion and maintenance therapy substantially increases total 25(OH)D and 25(OH)D2 despite a decrease in serum 25(OH)D3. This treatment program is an appropriate and effective strategy to treat and prevent vitamin D deficiency.(Endocr Pract. 2012;18:399-402) 相似文献
17.
Alba Hernández-Martín Tania González-García Margaret Lawlor Lesley Preston Vicente Gotor Susana Fernández Miguel Ferrero 《Bioorganic & medicinal chemistry》2013,21(24):7779-7789
C-3-substituted 25-hydroxyvitamin D3 analogues were synthesized as tools to directly measure levels of vitamin D in biological samples. The strategy involves vinyloxycarbonylation of the 3β-hydroxy group and formation of a carbamate bond with a hydroxyl or amino group at the end of the alkyl chain. Biotinylated conjugates of synthesized derivatives were generated to be linked with vitamin D binding protein (DBP). The spacer group present in the alkyl chain is important in the binding of antibodies to the analogue–DBP complex. When compared to 25-hydroxyvitamin D3-DBP, the binding of some antibodies to the analogue–DBP complex of the 25-hydroxyvitamin D3 derivative 10 that posses an 8-aminoctyl alkyl chain is significantly reduced, but this analogue displaced [26,27-3H]-25-hydroxyvitamin D3 from DBP. In contrast, the 8-hydroxyoctyl alkyl chain analogue 9 showed less displacement. 相似文献
18.
A single 325-pmol dose of 1,25-dihydroxyvitamin D3 given to chicks fed a vitamin D-deficient diet containing 3% calcium and 0.6% phosphorus suppresses renal mitochondrial 25-hydroxyvitamin D3-1α-hydroxylase and stimulates the 25-hydroxyvitamin D3-24-hydroxylase as measured by in vitro assay. This alteration in the enzymatic activity takes place over a period of hours. The administration of parathyroid hormone rapidly suppresses the 25-hydroxyvitamin D3-24-hydroxylase. The alterations in the hydroxylases by parathyroid hormone or 1,25-dihydroxyvitamin D3 are not related to changes in serum clacium or phosphate but could be related to changes in intracellular levels of these ions. Actinomycin D or cycloheximide given in vivo reduces the 25-hydroxyvitamin D3-24-hydroxylase activity rapidly which suggests that the turnover of the enzyme and its messenger RNA is rapid (1- and 5-h half-life, respectively). The half-lives of the hydroxylases are sufficiently short to permit a consideration that the regulation by 1,25-dihydroxyvitamin D3 and parathyroid hormone may involve enzyme synthesis and degradation. 相似文献
19.
Barbara E. Kream Robert D. Reynolds Joyce C. Knutson John A. Eisman Hector F. DeLuca 《Archives of biochemistry and biophysics》1976,176(2):779-787
The binding of 25-hydroxy-[26,27-3H]vitamin D3 and 1,25-dihydroxy-[26,27-3H]vitamin D3 to the cytosol of intestinal mucosa of chicks and rats has been studied by sucrose gradient analysis. The cytosol from chick mucosa showed variable binding of 1,25-dihydroxyvitamin D3 to a 3.0S macromolecule which has high affinity and low capacity for this metabolite. However, when the mucosa was washed extensively before homogenization, a 3.7S macromolecule was consistently observed which showed considerable specificity and affinity for 1,25-dihydroxyvitamin D3. Although 3.7S binders for 1,25-dihydroxyvitamin D3 could also be located in other organs, competition experiments with excess nonradioactive 1,25-dihydroxyvitamin D3 suggested that they were not identical to the 3.7S macromolecule from intestinal mucosal cytosol. As the 3.7S macromolecule was allowed to stand at 4 °C with bound 1,25-dihydroxy-[3H]vitamin D3, the 1,25-dihydroxy-[3H]vitamin D3 became increasingly resistant to displacement by non-radioactive 1,25-dihydroxyvitamin D3. The 1,25-dihydroxy-[3H]vitamin D3 remained unchanged and easily extractable with lipid solvents through this change, making unlikely the establishment of a covalent bond. Unlike the chick, mucosa from rats yielded cytosol in which no specific binding of 1,25-dihydroxy-[3H]vitamin D3 was detected. Instead, a 5-6S macromolecule which binds both 1,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3 was found. This protein which was also found in chick mucosa shows preferential binding for 25-hydroxyvitamin D3. It could be removed by washing the mucosa with buffer prior to homogenization which suggests that it may not be a cytosolic protein. Although the 3.7S protein from chick mucosa has properties consistent with its possible role as a receptor, the 5-6S macromolecule does not appear to have “receptor”-like properties. 相似文献
20.
R W Gray A E Caldas J L Weber J G Ghazarian 《Biochemical and biophysical research communications》1978,82(1):212-218
Vitamin D3-deficient chick kidney microsomes metabolize 25-hydroxy-[26(27)-methyl-3H]-vitamin D3 to yet structurally unidentified polar metabolites previously designated MIC-I and MIC-II. Kidney microsomes of vitamin D3-repleted chicks could not be demonstrated to produce these metabolites when 3H was the radioactive isotope in positions C-26 and C-27 of the substrate. However, when 25-hydroxy-[26,27-14C]-vitamin D3 was the radioactive substrate, MIC-I and MIC-II production was independent of the vitamin D3 status of the chicks. These results suggest that under conditions of vitamin D3-sufficiency, there is augmented sequential kidney metabolism of 25-hydroxyvitamin D3 to products with modified side-chains involving C-26 and/or C-27. It is possible that this metabolism is responsible for the regulation of kidney cellular concentrations of 25-hydroxyvitamin D3. 相似文献