scholarly journals The localization of 1,25-dihydroxycholecalciferol in bone cell nuclei of rachitic chicks

1971 ◽  
Vol 125 (1) ◽  
pp. 147-153 ◽  
Author(s):  
J. C. Weber ◽  
V. Pons ◽  
E. Kodicek
Keyword(s):  
Vitamin D ◽  
Subcellular Distribution ◽  
Time Course ◽  
Supernatant Fraction ◽  
Intestinal Cell ◽  
Nuclear Fraction ◽  
Vitamin D Metabolites ◽  
Cell Nuclei ◽  
Polar Metabolite ◽  
25 Hydroxycholecalciferol

1. A simple technique has been developed to obtain subcellular fractions of chick bone. The method yielded 60–70% of total DNA in the nuclear debris fraction and 80–90% of total 14C recovered in bone after a dose of radioactive vitamin D. 2. After a dose of [4-14C,1,2-3H2]cholecalciferol (0.5μg) was given to vitamin D-deficient chicks, the time-course of total 14C radioactivity in the epiphysis, metaphysis and diaphysis of proximal tibiae was measured. The maximum concentrations were reached at 6h, corresponding to a similar peak of radioactivity in blood, decreasing until 24h and indicating the dependence on the circulating 14C and on the blood supply of the three bone components. 3. The 14C radioactivity of cholecalciferol and 25-hydroxycholecalciferol (expressed per mg of DNA) followed the pattern of incorporation of total 14C radioactivity in all three bone components. The more polar metabolite fraction reached a peak of radioactivity at 6–9h and maintained its concentration over the 24h period studied in all anatomical bone components. 4. After a dose of [4-14C,1-3H]cholecalciferol (0.5μg) was given to vitamin D-deficient chicks, the subcellular distribution was studied. At 24h after dosing, the nuclear fraction contained 27% and the supernatant fraction had 67% of total 14C recovered in the bone filtrate. When the 14C in the residual bone fragments was included, the nuclear fraction contained up to 35% of the total radioactivity in the bone. 5. The subcellular distribution pattern of individual vitamin D metabolites indicated that the purified nuclear fraction concentrated the polar metabolite, which lost 3H at C-1, so that 77% of the radioactivity could be accounted for by 1,25-dihydroxycholecalciferol. The supernatant fraction contained smaller amounts of 1,25-dihydroxycholecalciferol (9%), with 66% of 25-hydroxycholecalciferol forming the major metabolite, corresponding to its concentration found in blood at 24h. 6. The preferential accumulation of 1,25-dihydroxycholecalciferol in the nuclear fraction and the overall pattern of other metabolites, found previously in intestinal tissue, suggests a similar mechanism of action in bone to that postulated for the intestinal cell in calcium translocation.

scholarly journals Effects of vitamin D on calcium regulation in vitamin-D-deficient pigs given a phytate-phosphorus diet

1986 ◽  
Vol 56 (3) ◽  
pp. 661-669 ◽  
Author(s):  
A. Pointillart ◽  
Nicole Fontaine ◽  
Monique Thomasset
Keyword(s):  
Vitamin D ◽  
Alkaline Phosphatase ◽  
Time Course ◽  
Mineral Metabolism ◽  
Calcium Balance ◽  
Vitamin D Metabolites ◽  
Vitamin D Metabolism ◽  
Phytate Phosphorus ◽  
Diet Regimen ◽  
25 Hydroxycholecalciferol

1.Vitamin-D-deficient pigs were fed on a phytate-phosphorus diet and treated with vitamin D, (+D) to examine the time-course of adaptative changes in plasma minerals, vitamin D metabolites, parathyroid hormone (PTH) and calcium balance and intestinal Ca-binding protein (CaBP).2. The 5-week vitamin D repletion (25 μg cholecalciferol/kg diet) regimen restored plasma Ca, P and alkaline phosphatase (EC 3.1.3.1) to normal, decreased PTH and markedly and rapidly increased plasma 25- hydroxycholecalciferol (25-OHD, sevenfold after 4 d) and 1, 25-dihydroxycholecalciferol ( 1, 25(OH)2D3, 1.8-fold after 4 d).3. CaBP concentrations were markedly elevated all along the digestive tract, especially in the distal regions.4. Ca absorption and retention were enhanced (fourfold and sixfold respectively) by the +D diet.5. The improved Ca absorption, coupled with increased CaBP and 1, 25(OH)2D3 levels, suggest that vitamin D metabolism in phytate-P-fed pigs is sensitive to the depressed Ca availability due to phytate feeding. It also indicates that CaBP may play an important role in the adaptation of Ca absorption.6. Persistent hypercalciuria indicates that mineral metabolism was still affected by the phytate nature of the dietary P in spite of the vitamin D treatment.

The Adenylate Cyclase System in Human Liver: Characterization, Subcellular Distribution and Hormonal Sensitivity in Normal or Cirrhotic Adult, and in Foetal Liver

1979 ◽  
Vol 57 (4) ◽  
pp. 313-325 ◽  
Author(s):  
F. Pecker ◽  
P. Duvaldestin ◽  
P. Berthelot ◽  
J. Hanoune
Keyword(s):  
Adenylate Cyclase ◽  
Subcellular Distribution ◽  
Human Liver ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Supernatant Fraction ◽  
Nuclear Fraction ◽  
Adenylate Cyclase System ◽  
Adult Liver ◽  
Foetal Liver

1. Adenylate cyclase (EC 4.6.1.1) activity was characterized in human liver, and its subcellular distribution compared with that of three other potential enzyme markers of the pericellular membrane: leucine aminopeptidase (EC 3.4.11.1), γ-glutamyltransferase (EC 2.3.2.2) and 5′-nucleotidase (EC 3.1.3.5). Although these three enzyme activities were detected in each of the subcellular fractions studied, 85% of the total adenylate cyclase activity was found in the 1000 g pellet (‘nuclear’ fraction) with a threefold increase in specific activity as compared with the homogenate. No adenylate cyclase activity existed in the 150 000 g supernatant fraction. 2. In the ‘nuclear’ fraction, adenylate cyclase activity was increased in a dose-dependent fashion by glucagon with a half-maximal stimulation at 10 nmol/l and a maximal four- to seven-fold increase at 1 μmol/l. Catecholamines activated adenylate cyclase 2·5- to three-fold, with an order of potency (protokylol > isoprenaline > adrenaline > noradrenaline) typical of a β2-adrenoreceptor. Prostaglandin E1 and NaF also stimulated cyclase two- and four-fold respectively. Insulin, serotonin, dopamine, thyroid-stimulating hormone and ACTH had no effect. Adenosine provoked a weak inhibition at 0·1 mmol/l. Finally guanosine triphosphate and 5′-guanylyl imidodiphosphate induced a marked increase in basal activity, four- and eight-fold respectively, but both reduced the relative increase in enzyme activity due to glucagon or adrenaline. 3. Cyclase from foetal liver (12–16 weeks old) and cirrhotic adult liver appeared to behave similarly to that from normal liver; however, foetal cyclase was more active, and cirrhotic enzyme less active than normal adult liver. Both systems responded to catecholamines via a β2-adrenoreceptor. 4. These results validate the use of rat liver adenylate cyclase as a tool for pharmacological and physiological studies.

New Vitamin D Metabolite localized in Intestinal Cell Nuclei

Nature ◽  
1969 ◽  
Vol 222 (5189) ◽  
pp. 171-172 ◽  
Author(s):  
D. E. M. LAWSON ◽  
P. W. WILSON ◽  
E. KODICEK
Keyword(s):  
Vitamin D ◽  
Intestinal Cell ◽  
Cell Nuclei

scholarly journals Metabolism of vitamin D. A new cholecalciferol metabolite, involving loss of hydrogen at C-1, in chick intestinal nuclei

1969 ◽  
Vol 115 (2) ◽  
pp. 269-277 ◽  
Author(s):  
D. E. M. Lawson ◽  
P. W. Wilson ◽  
E. Kodicek
Keyword(s):  
Vitamin D ◽  
Adipose Tissue ◽  
Maximum Concentration ◽  
Simultaneous Administration ◽  
Polar Material ◽  
Polar Metabolite ◽  
Chemical Structures ◽  
Intracellular Organelle ◽  
Liver And Kidney ◽  
25 Hydroxycholecalciferol

1. A comparison was made of the nature and intestinal intracellular distribution of the metabolites formed in vitamin D-deficient chicks from [4−14C]cholecalciferol and [1−3H]cholecalciferol. 2. The simultaneous administration of the two radioactive substances showed the presence in blood, liver, intestine, kidney and bone of cholecalciferol, its ester, 25-hydroxycholecalciferol and a further metabolite of cholecalciferol more polar than 25-hydroxycholecalciferol. The 3H/14C ratios in these four radioactive components were the same as that of the dosed material (4·7:1) with the exception of the most polar material. The 3H/14C ratio was lower in the fourth, most polar, metabolite (0·4:1–1·8:1) in all tissues examined, with the exception of blood. 3. In the chick intestine the polar metabolite accounted for almost 70% of the radioactivity in this tissue after a dose of 0·5μg. of [4−14C,1−3H]cholecalciferol. This polar metabolite from the intestine also had the lowest 3H/14C ratio of all the tissues. It appears that in the chick intestine the polar metabolite reaches a maximum concentration of 1ng./g. of tissue, above which it cannot be increased irrespective of the dose of the vitamin. 4. The intestinal intracellular organelle with the highest concentration of 14C radioactivity is the nucleus, and this radioactivity is almost entirely due to the polar metabolite with the lowered 3H/14C ratio, in this case <0·2:1. It appears to be further localized in the chromatin of the nuclei. However, about half of the polar metabolite in the intestine is extranuclear. 5. Double-labelled 25-hydroxycholecalciferol was prepared and after its administration to vitamin D-deficient chicks the polar metabolite with the lowered 3H/14C ratio was detected in liver, kidney, intestine, bone, muscle and heart. 6. None of the polar metabolite with the lowered 3H/14C ratio was detected 16hr. after dosing with either the double-labelled vitamin or the double-labelled 25-hydroxycholecalciferol in blood and adipose tissue of vitamin D-deficient chicks, nor in the intestine, liver and kidney of supplemented birds. 7. The reasons for this loss of 3H relative to 14C are discussed in relation to possible chemical structures of this new polar metabolite.

scholarly journals Influence of Secondary Hyperparathyroidism Induced by Low Dietary Calcium, Vitamin D Deficiency, and Renal Failure on Circulating Rat PTH Molecular Forms

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Pierre D'Amour ◽  
Louise Rousseau ◽  
Stephen Hornyak ◽  
Zan Yang ◽  
Tom Cantor
Keyword(s):  
Vitamin D ◽  
Renal Failure ◽  
Secondary Hyperparathyroidism ◽  
Time Course ◽  
Normal Diet ◽  
Molecular Forms ◽  
Vitamin D Metabolites ◽  
Short Time ◽  
The Relationship ◽  
Normal Calcium

Rats(r) with secondary hyperparathyroidism were studied to define the relationship between vitamin D metabolites and rPTH levels measured by 3 different rat ELISAs. Controls and renal failure (RF) rats were on a normal diet, while 2 groups on a low-calcium (-Ca) or a vitamin D-deficient (-D) diet. RF was induced surgically. Mild RF rats had normal calcium and 25(OH)D but reduced 1,25(OH)2D levels (P<.001) with a 2.5-fold increased in rPTH (P<.001). Severe RF rats and those on a -Ca or -D diet had reduced calcium (P<.01) and 25(OH)D levels (P<.05), with rPTH increased by 2 (-Ca diet;P<.05), 4 (-D diet;P<.001), and 20-folds (RF;P<.001) while 1,25(OH)2D was high (-Ca diet:P<.001) or low (-D diet, RF:P<.001). 25(OH)D and 1,25(OH)2D were positively and negatively related on the -Ca and -D diets, respectively. rPTH molecular forms behaved as expected in RF and on -Ca diet, but not on -D diet with more C-rPTH fragments when less were expected. This may be related to the short-time course of this study compared to prior studies.

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