Induction of 25-OH-vitamin D3 24- and 23-hydroxylase activities in partially purified renal extracts from pigs given exogenous 1,25-(OH)2D3

A renal mitochondrial cytochrome P 450 preparation from pigs treated with exogenous 1,25-(OH)2D3 was reconstituted with an NADPH-generating system, adrenodoxin and adrenodoxin reductase. The reconstituted system catalyzed the conversion of the substrate, 25-OH-D3, to metabolites comigrating with authentic 23,25-(OH)2D3 and 24,25-(OH)2D3 in both straight- and reverse-phase high-performance liquid chromatography systems, which achieve separation of these metabolites from each other as well as from other vitamin D metabolites. The putative 23,25-(OH)2D3 product was resistant to periodate treatment, while the 24,25-(OH)2D3 product was sensitive, providing additional evidence for the identity of the products. Although induction of 24-hydroxylase activity has been studied using renal homogenates from several species, only recently have techniques become available to study the activity of the enzyme in a solubilized and reconstituted form. Using these techniques, the present study shows that production of 24,25-(OH)2D3 was increased more than 80-fold with 1,25-(OH)2D3 treatment compared with untreated controls, an effect much greater than that previously observed with homogenates. In addition, production of both 23,25-(OH)2D3 and 24,25-(OH)2D3 varied with substrate concentration and was consistent with a monooxygenase-linked enzyme reaction.     

Kidney microsomal metabolism of 25-hydroxyvitamin D3+.

Vitamin D₃-deficient chick kidney microsomes $\text{in vitro}$ metabolize 25-hydroxyvitamin D₃ to two polar metabolites by a pathway which may involve side-chain modification. Molecular oxygen and a source of reduced nicotinamide adenine dinucleotide phosphate are required for this metabolism. Kidney cytosol obtained from deficient chicks or kidney microsomes of vitamin D₃-repleted chicks do not metabolize 25-hydroxyvitamin D₃. The two products are tentatively designated MIC-I and MIC-II.     

莫扎特K448奏鸣曲高频段声波对小鼠抑郁模型干预治疗的分析

目的 建立C57BL/6小鼠抑郁模型,初步探究莫扎特K448奏鸣曲中的高频段声波改善C57BL/6小鼠抑郁症状的效果。方法 1)慢性应激模型的建立:小鼠依据自主活动实验结果剔除活动次数差异较大者,其余分为空白组(n=10)、模型组(n=36),模型组经历5周慢性温和不可预知刺激(chronic unpredictable and mildstress,CUMS),建立小鼠抑郁模型。(2)治疗干预:造模成功后,将模型组小鼠随机均衡分为模型对照组(n=12)、氟西汀组(n=12)和音乐组(n=12)。氟西汀组每天腹腔注射盐酸氟西汀溶液(10 mg/kg),其余两组注射等量的生理盐水。音乐组每天进行2 h高频音乐干预,其余两组不进行音乐干预。干预持续2周。(3)效果评价:实验前3 d及实验中每周称量体重并记录,实验第1周、第5周、第7周进行悬尾实验(tail suspension test,TST)和强迫游泳实验(forced swimming test,FST)。第7周行为学实验结束后,取小鼠脑组织制备匀浆,通过酶联免疫吸附法(enzymelinked immunosorbent assay,ELISA)测定脑源性神经营养因子(brain derived neurotrophic factor,BDNF)含量。结果1)成功构建CUMS小鼠模型。第5周模型组小鼠悬尾不动时间明显增加,差异有显著性(P<0.01),强迫游泳不动时间增加,差异有显著性(P<0.05)。(2)氟西汀组与模型对照组相比,悬尾实验不动时间明显缩短,差异有显著性(P<0.01),强迫游泳实验不动时间缩短,差异无显著性(P>0.05);音乐组与模型对照组相比,悬尾不动时间缩短,差异有显著性(P<0.05),强迫游泳实验不动时间无明显改变,差异无显著性(P>0.05)。模型对照组与空白组小鼠相比,脑组织匀浆中的BDNF含量明显降低,差异有显著性(P<0.01);氟西汀组与模型对照组相比,脑组织匀浆中的BDNF含量明显回升,差异有显著性(P<0.01),但音乐组与模型对照组相比,其差异无显著性(P>0.05)。结论 莫扎特K448奏鸣曲高频段声波可一定程度优化小鼠抑郁模型的治疗作用。     

Purification and characterization of the ferredoxin component of 25-hydroxycholecalciferol 1 alpha-hydroxylase.

The chick kidney mitochondrial iron--sulphur protein (ferredoxin), a component of the NADPH--cytochrome P-450 reductase functional in the 1 alpha-hydroxylation of 25-hydroxycholecalciferol, was purified to homogeneity by chromatography on DEAE-cellulose, gel filtration on Sephadex G-100 and preparative electrophoresis on polyacrylamide gel. A novel NADPH--cytochrome c reductase assay utilizing crude renal NADPH--ferredoxin reductase was used for the detection of the ferredoxin. A mol. wt. of 53 000 was determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and by Sephadex G-100 gel filtration of the 125I-labelled ferredoxin. The ferredoxin has a sedimentation constant (S 20, w) of 2.66S, an A411/A280 of 0.4, and a molar absorptivity of 7300 cm-1 . M-1. The electron-paramagnetic-resonance spectrum after reduction with Methyl Viologen and dithionite was characteristic of ferredoxins with signals at g = 1.956 and 2.025. Two iron and two labile sulphur atoms per molecule of ferredoxin were released by acid. Ouchterlony immunodiffusion tests by using goat anti-(bovine adrenal ferredoxin) antiserum showed precipitin reactions with the bovine adrenal ferredoxin and the chick renal ferredoxin as antigens, suggesting that the renal ferredoxin shares antigenic determinants(s) with the natural adrenal antigen. Amino acid analysis showed that of the total number of residues per molecule of ferredoxin, glutamic acid and aspartic acid are the most abundant residues, comprising 17 and 15% respectively.     

Phosphorylation of ferredoxin and regulation of renal mitochondrial 25-hydroxyvitamin D-1 alpha-hydroxylase activity in vitro

The kidney is the principal physiologic site of production of biologically active 1,25-dihydroxyvitamin D. The 25-hydroxyvitamin D-1 alpha-hydroxylase (1-OHase) activity found in renal mitochondria is under tight hormonal control. Parathyroid hormone stimulates the renal conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D in young animals, which is accompanied by dephosphorylation of ferredoxin (Fx), a component of the mitochondrial 1-OHase enzyme complex (Siegel, N., Wongsurawat, N., and Armbrecht, H. J. (1986) J. Biol. Chem. 261, 16998-17003). The present study investigates the capacity of Fx to be phosphorylated in vitro and to modulate the 1-OHase activity of a reconstituted system. Fx was phosphorylated by renal mitochondrial type II protein kinase. Phosphorylation did not alter Fx mobility on sodium dodecyl sulfate gels but did decrease the pI as measured by isoelectric focusing. Amino acid analysis demonstrated that 1 mol of serine and 1 mol of threonine were phosphorylated per mol of Fx. Peptide mapping of phosphorylated Fx was consistent with phosphorylation of serine 88 and threonine 85 or 97. Fx was selectively dephosphorylated by rabbit skeletal muscle protein phosphatase C2 but not C1. Phosphorylation of Fx significantly inhibited the 1-OHase activity of a reconstituted system consisting of Fx reductase, Fx, and renal mitochondrial cytochrome P-450. These findings suggest that phosphorylation/dephosphorylation of Fx may play a role in modulating renal 1,25-dihydroxyvitamin D production.     

Chick kidney microsomal cytochrome P-450 involvement in the metabolism of 25-hydroxyvitamin D3

Suspensions of 2 to 5% rat thymocytes were incubated at 35 °C in buffered balanced salt solution (pH 7.3) with lactate and β-hydroxybutyrate as fuels. The dependence of 3-O-[Me-³H]methylglucose influx on external and internal 3-O-methylglucose concentrations was studied. Entry was almost rectilinear during the first minute. From the dependence of methylglucose entry (into sugar-free cells) on external methylglucose concentration, we judged the entry K_m to be about 7.7 mm and the entry V to be about 0.64 μmol · min^?1 · (ml of packed cell volume)^?1. Methylglucose inside the cell enhanced influx, hence equilibrium exchange was faster than entry. The dependence of equilibrium exchange on methylglucose concentration (inside and outside being equal) indicated a K_m of about 25 mm and a V of about 2.1 μmol · (min)^?1 · (ml of cell volume)^?1. This effect of internal sugar indicated that entry into sugar-free cells is limited mainly by the return of empty carrier to the outside surface and that loading the carrier on the inside enhances its outward mobility. The K_m and V for influx into cells containing 21 mm methylglucose were 5.9 mm and 1.17 μmol · min^?1 · (ml of packed cells)^?1. The effect of 21 mm internal sugar on lowering the influx K_m from about 7.7 mm to about 6 mm was reproducible and contributed to the evaluation of the constants of the transport rate law. It indicated that loading of the carrier at the external surface reduces its mobility, in contrast to the effect of loading on the inside. Mechanical explanations for this behavior are discussed.