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At least 19 recordsLinked to original sources
PubMed1976

High-performance liquid chromatographic analysis of vitamins I: quantitation of cholecalciferol or ergocalciferol in presence of photochemical isomers of the provitamin and application to cholecalciferol resins.

A high-performance liquid chromatographic (HPLC) procedure was developed for the quantitative determination of cholecalciferol or ergocalciferol in the presence of the photochemical isomers of the provitamin. Separation is also achieved from various common reaction products encountered in the vitamin synthesis as well as other fat-soluble vitamins. The method was applied to the routine analysis of cholecalciferol resins, and experimental data are set forth. A comparison of the HPLC method to the AOAC biological and chemical procedures shows that the HPLC method most closely approximates the antirachitic activity of a cholecalciferol sample. The specificity, sensitivity, and reproducibility of the method make it applicable to various vitamin samples containing cholecalciferol or ergocalciferol.

Biological Assay↗
PubMed1978

Incorportion of oxygen-18 into the 25-position of cholecalciferol by hepatic cholecalciferol 25-hydroxylase.

The oxygen enzymically inserted as a hydroxy function by rat liver post-mitochondrial fraction into the 25-position of cholecalciferol to giver 25-hydroxycholecaliferol is derived exclusively from molecular O2. Therefore like the other two cholecalciferol hydroxylases, i.e. 25-hydroxycholecalciferol 1alpha-hydroxylase and 25-hydroxycholecalciferol 24-hydroxylase, the cholecalciferol 25-hydroxylase is also a mono-oxygenase ('mixed-function oxidase').

Animals↗
PubMed1978

Comparative studies on the 25-hydroxylations of cholecalciferol and 1 alpha-hydroxycholecalfierol in perfused rat liver.

The 25-hydroxylations of [(3)H]cholecalciferol and 1alpha-hydroxy[(3)H]cholecalciferol in perfused rat liver were compared. Results showed that about twice as much 1alpha(OH)D(3) (1alpha-hydroxycholecalciferol) was incorporated into the liver as cholecalciferol. 25-Hydroxy[(3)H]cholecalciferol and 1alpha-25-dihydroxy[(3)H]cholecalciferol were not incorporated significantly. Livers isolated from vitamin D-deficient rats formed the 25-hydroxy derivatives of cholecalciferol and 1alpha(OH)D(3) respectively linearly with time for at least 120min. The rate of 1alpha,25(OH)(2)D(3) (1alpha,25-dihydroxycholecalciferol) production increased exactly 10-fold on successive 10-fold increases in the dose of 1alpha(OH)D(3), suggesting that hepatic 25-hydroxylation of 1alpha(OH)D(3) is not under metabolic control. On the other hand, the rate of conversion of cholecalciferol into 25(OH)D(3) (25-hydroxycholecalciferol) did not increase linearly with increase in the amount of cholecalciferol in the perfusate. The 25-hydroxylation of cholecalciferol seemed to proceed at a similar rate to that of 1alpha(OH)D(3) at doses of less than 1nmol, but with doses of more than 2.5nmol, the conversion of cholecalciferol into 25(OH)D(3) became much less efficient, though the linear relation between the amounts of substrate and product was maintained. A reciprocal plot of data on the 25-hydroxylation of cholecalciferol gave two K(m) values of about 5.6nm and 1.0mum, whereas that for the 25-hydroxylation of 1alpha(OH)D(3) gave a single K(m) value of about 2.0mum. These results suggest that there are two modes of 25-hydroxylation of cholecalciferol in the liver, which seem to be closely related to the mechanism of control of 25(OH)D(3) production by the liver.

Animals↗
PubMed1978

Synthesis of 1 alpha-hydroxy[7-3H]cholecalciferol and its metabolism in the chick.

1. 1 alpha-Hydroxy[7-3H]cholecalciferol (specific radioactivity of 2-Ci/mmol) was synthesized, and its metabolism in chicks studied. 2. 1 alpha-Hydroxy[7-3H]cholecalciferol was metabolized very rapidly in the chick to 1 alpha,25-dihydroxy[7-3H]cholecalciferol and to a metabolite less polar than 1 alpha-hydroxycholecalciferol. Intestine exhibited highest accumulation of 1 alpha-25-dihydroxy[7-3H]cholecalciferol, and liver exhibited highest accumulation of the non-polar metabolite. 3. Tissue uptake of 1 alpha-hydroxy[7-3H]cholecalciferol and its metabolites in chicks that were dosed continuously for 16 days with 1 alpha-hydroxy[7-3H]cholecalciferol did not exceed by very much that observed in tissues obtained from chicks that were dosed with a single injection of 1 alpha-hydroxy[7-3H]cholecalciferol 24 h before killing, except for liver and kidney. 4. Lowest accumulation of metabolites was noted in muscle and bone, and for the latter, highest uptake of 1 alpha,25-dihydroxy[7-3H]cholecalciferol was noted in the epiphysial periosteum and the metaphysis. 5. Formation of 1 alpha,24,25-trihydroxy[7-3H]cholecalciferol was not observed in the chicks that were dosed continuously with 1 alpha-hydroxy[7-3H]cholecalciferol, despite the fact that plasma calcium and phosphorus were normal and despite the presence of renal 24-hydroxylase activity. 6. The vitamin D status of the chicks did not appear to affect the metabolic profile of the administered 1 alpha-hydroxy[7-3H]cholecalciferol.

Animals↗
PubMed1979

Quantitative studies of the interaction of cholecalciferol ((vitamin D3) and its metabolites with different genetic variants of the serum binding protein for these sterols.

Cholecalciferol (vitamin D3) and its 25-hydroxy metabolite are transported in plasma bound to a specific protein, the binding protein for cholecalciferol and its metabolites (DBP). DBP is identical with the group-specific component (Gc) proteins, which are known to display genetic polymorphism. Studies were conducted to explore whether or not major differences in the transport of cholecalciferol and its biological metabolites might exist among persons with different Gc phenotypes. Detailed quantitative studies were first carried out on the interaction of 25(OH)D3 with DBP in 21 different samples of serum, representing eight different Gc phenotypes. The studies used a filter disc assay method that provided highly reproducible quantitative results with cholecalciferol-related sterols. The Gc phenotypes studied included the three common types (Gc 1-1, 2-1, and 2-2) and several uncommon genetic variants (Gc Ab-Ab, Ab-1, Ab-2, Chip-1, and Chip-2). The binding affinities for 25(OH)D3 observed with these different sera were all fairly similar to each other. More extensive studies were then conducted to compare the binding of four cholecalciferol-related sterols to each of three genetic variants of DBP, by using sera from homozygous persons with the Gc 1-1, Gc 2-2 and Gc Ab-Ab phenotypes. The ligands tested included cholecalciferol, 25(OH)D3, 1,25(OH)2D3, and 24(R) 25(OH)2D3. The affinities of the three genetic types of DBP/Gc protein were found to be similar for each of the four cholecalciferol-related sterols. The apparent association constants for 25(OH)D3 and 24,25(OH)2D3 were similar (approx. 1--2 x 10(8) M-1); lesser affinities were observed for 1,25(OH)2D3 (kA approx. 1 x 10(7) M-1) and for cholecalciferol (kA approx. 3--4 x 10(5) M-1). Thus the common genetic variants of DBP/Gc protein, and the uncommon genetic variants studied here, all appear to have similar binding properties for cholecalciferol and its several metabolites.

Alpha-Globulins↗
PubMed1992

Studies to determine whether an interaction exists among boron, calcium, and cholecalciferol on the skeletal development of broiler chickens.

Two experiments were designed to determine the effect of dietary boron on broiler cockerels and four experiments were conducted to determine whether an interaction exists among dietary boron, cholecalciferol, and calcium. The parameters measured were weight gain, feed efficiency, tibia bone ash, rickets, tibial dyschondroplasia, and plasma minerals. All experiments were conducted with tibial dyschondroplasia-inducing basal diets fed to broiler cockerels from 1 to 16 days of age. Experiments 1 and 2 had four levels of dietary boron (0, 20, 40, and 80 mg/kg (Experiment 1) and 0, 5, 10, and 20 mg/kg (Experiment 2). Boron had no effect on weight gain, feed efficiency, or plasma minerals in either experiment. In Experiment 2, increasing levels of boron had no influence on tibial dyschondroplasia but did exert a quadratic effect on bone ash with 5 and 10 mg/kg boron increasing bone ash. In Experiment 1, bone ash and the incidence of tibial dyschondroplasia were unaffected, but the severity of tibial dyschondroplasia linearly increased by increasing boron levels. Experiments 3 to 6 had a 2 x 2 x 2 factorial arrangement of treatments with calcium at .65 and .90%, cholecalciferol at 110 and 1,100 ICU/kg, and boron at 0 and 40 mg/kg (Experiments 3 to 5) or 0 and 3 mg/kg (Experiment 6). The higher levels of calcium and cholecalciferol improved weight gain, decreased the incidence of rickets, and decreased the incidence and severity of tibial dyschondroplasia. Feeding cholecalciferol at 1,100 ICU/kg increased plasma calcium and plasma dialyzable phosphorus and decreased plasma magnesium. Calcium at .90% had no effect on plasma magnesium or plasma dialyzable phosphorus and increased plasma calcium only in Experiment 4. The only response to boron in Experiments 3 to 6 was a boron effect and a boron by cholecalciferol interaction on bone ash in Experiment 3, in which boron reduced bone ash at .65% calcium and 110 ICU/kg cholecalciferol. From these experiments, there is no indication that an interaction among boron, cholecalciferol, and calcium exists in broiler cockerels.

Animal Feed↗
PubMed1975

Effects of cholecalciferol on the translocation of calcium by non-everted chick ileum in vitro.

An apparatus is described that allows perfusion of a non-everted segment of intestine in vitro and the study of the accumulation of substances within the mucosal cells. The translocation of Ca(2+) by rachitic-chick ileum and the effect of pretreatment with cholecalciferol was investigated, with the following conclusions. (1) Entry of Ca(2+) across the microvilli into mucosal cells is by diffusion; it does not require metabolic energy or the presence of any other inorganic ions. (2) Pretreatment of the chick with cholecalciferol causes increased permeability of the microvillus to Ca(2+) in both directions (lumen to cell, cell to lumen). The increased transport brought about by cholecalciferol in vivo can be partially mimicked by sodium dodecyl sulphate added in vitro. (3) The sign and the magnitude of the electrical potential difference prevailing across the ileum does not influence Ca(2+) transport. (4) Exit of Ca(2+) from the mucosal cell is temperature-sensitive, requires metabolic energy and Na(+). (5) Pretreatment with cholecalciferol caused increased movement of Ca(2+) out of the cell across the basement membranes. This effect of cholecalciferol given in vivo could be markedly increased by the presence of dicyclohexylcarbodi-imide in the perfusion fluid. These observations suggested that cholecalciferol increased Ca(2+) entry (and exit) at the mucosal surface and also caused Ca(2+) to be more available to the pump at the serosal surface.

Anaerobiosis↗
PubMed1979

Characteristics of the rat liver microsomal enzyme system converting cholecalciferol into 25-hydroxycholecalciferol. Evidence for the participation of cytochrome p-450.

Properties of the rat hepatic cholecalciferol 25-hydroxylase have been studied. An assay system has been developed in which 25-hydroxycholecalciferol production is linear for at least 2h in both homogenates and microsomal fraction. Furthermore, the initial reaction velocity is linearly related to the amount of liver tissue or microsomal fraction. This enzyme system also metabolizes an analogue of cholecalciferol, namely dihydrotachysterol 3, into 25-hydroxydihydrotachysterol 3. The 25-hydroxylase is in the microsomal fraction and not in mitochondria. It has a Km of 44 nM for cholecalciferol and 360 nM for dihydrotachysterol 3. Its activity is not altered by dietary concentrations of calcium and phosphorus. Vitamin D-deficient rats have higher activities of the hepatic 25-hydroxylase than those receiving 25 ng of cholecalciferol daily. The 25-hydroxylase is inhibited by metyrapone. An atmosphere of CO/O2 (9:1, v/v) inhibits the reaction by 87%. This inhibition is partially reversed by white light. Additionally, cholecalciferol and 25-hydroxycholecalciferol competitively inhibit aminopyrine demethylase. These results support the idea that the cholecalciferol 25-hydroxylase is a cytochrome P-450-dependent mono-oxygenase.

Animals↗
PubMed1978

Intestinal cholecalciferol absorption in the elderly and in younger adults.

1. A method for assessing cholecalciferol absorption in man is described. 2. The intestinal absorption of [3H]cholecalciferol was studied in 20 female geriatric patients, most of whom were vitamin D-depleted. 3. The plasma [3H]cholecalciferol response after oral ingestion was significantly lower than that of a group of younger female subjects. 4. The plasma response of labelled polar metabolites of cholecalciferol was also lower in the geriatric than in the younger group, suggesting that increased removal of label by conversion into more polar metabolites could not account for the reduced plasma [3H]cholecalciferol response. 5. There was no evidence that alteration in gastrointestinal motility could account for the different rate of appearance of the labelled vitamin in the plasma in the two groups. 6. It is suggested that there is a defect in intestinal absorption of cholecalciferol in the elderly.

Adult↗
PubMed1979

Intestinal absorption of cholecalciferol in alcoholic liver disease and primary biliary cirrhosis.

The intestinal absorption of (3H)cholecalciferol was studied in five patients with alcoholic liver disease, six patients with primary biliary cirrhosis, and 15 healthy subjects. The rate of appearance in plasma of (3H)cholecalciferol after oral ingestion and the subsequent appearance of (3H) polar metabolites in the alcoholic subjects were similar to those in the healthy subjects. In subjects with primary biliary cirrhosis the rate of appearance in plasma of (3H)cholecalciferol was significantly reduced. The rate of appearance of labelled polar metabolites of cholecalciferol was also lower in this group, suggesting that increased removal of labelled vitamin by conversion into more polar metabolites could not account for the reduced plasma (3H)cholecalciferol response. It is suggested that intestinal absorption of cholecalciferol is usually normal in alcoholic liver disease but impaired in primary biliary cirrhosis. Hepatic 25-hydroxylation is normal in alcoholic liver disease but may be defective in primary biliary cirrhosis.

Adult↗
PubMed1979

Metabolism of cholecalciferol in land snails.

1. Radioactively labelled cholecalciferol was injected into the land snails Levantina hiersolyma and Theba pisana. Three metabolites (C, D and E), more polar than cholecalciferol, were found. 2. Metabolite C was found to be identical with 25-hydroxycholecalciferol. On injection of 25-hydroxy[26,27-3H]cholecalciferol, metabolite E was predominantly formed. Metabolite D was predominantly formed from cholecalciferol. Metabolites D and E differ from any known cholecalciferol metabolites. 3. The intestine was found to be the tissue capable of carrying out the transformation of 25-hydroxycholecalciferol into metabolite E. 4. 25-Hydroxycholecalciferol and metabolite E were localized in the digestive gland of the snail, the tissue responsible for the absorption of Ca2+ and its storage. Metabolite D was not localized in any specific tissue.

Animals↗
PubMed1977

Changes in plasma 25-hydroxycholecalciferol and selected blood parameters after injection of massive doses of cholecalciferol or 25-hydroxycholecalciferol in non-lactating dairy cows.

Plasma levels of 25-hydroxycholecalciferol, free hydroxyproline, calcium, phosphorus, and magnesium were determined in non-lactating, pregnant dairy cows injected intra-muscularly with 15 X 10(6) IU of cholecalciferol or 25 mg of 25-hydroxycholecalciferol. A lag in the conversion of cholecalciferol to 25-hydroxycholecalciferol was observed in the cows injected with cholecalciferol, while an immediate increase was observed when cows were injected with 25-hydroxycholecalciferol directly. The increased plasma levels of 25-hydroxycholecalciferol following injection of cholecalciferol were directly related to rises in plasma free hydroxy-proline, calcium, and phosphorus, while plasma magnesium was inversely related to plasma 25-hydroxycholecalciferol. Injection of 25-hydroxycholecalciferol caused an immediate increase in plasma calcium which persisted for the duration of the experiment. The biological half-life of 25-hydroxycholecalciferol in the injected cows was found to be 34 days. The data indicate the possibility of a feedback mechanism in which massive doses of cholecalciferol inhibit hydroxylation at the 25ths carbon preventing its conversion to 25-hydroxycholecalciferol until after 8 days post injection. The increase in plasma 25-hydroxycholecalciferol after 8 days resulted in increased bone resorption as indicated by plasma free hydroxyproline.

Animals↗
PubMed1992

Cardiovascular risk factors during estrogen-norethindrone and cholecalciferol treatment.

The effect of cholecalciferol and estrogen-norethindrone treatment on total cholesterol level, high-density lipoprotein cholesterol level, blood pressure, and body mass index was investigated in 74 postmenopausal women in a double-blind, randomized trial. Blood pressure and body mass index did not change throughout the study. We demonstrated a decrease (11%) in serum cholesterol level after 1 year of treatment with estrogen-norethindrone. When this treatment was combined with cholecalciferol, a similar decrease (13%) was observed. The hypocholesterolemic effect was correlated to body mass index in a way that indicated the most pronounced decrease in lean women. The high-density lipoprotein cholesterol/total cholesterol fraction increased by 45% after 1 year of estrogen-norethindrone treatment, while an increase of 25% after 1 year was seen when cholecalciferol was added to the treatment. The latter increase was not different from a similar increase in the placebo group. The possible dyslipidemic effect of cholecalciferol, along with the risk of hypercalcemia, emphasizes the caution necessary in cholecalciferol treatment.

Aged↗
PubMed1979

The metabolism of cholecalciferol in the liver of Japanese quail (Coturnix coturnix japonica) with particular reference to the effects of oestrogen.

1. Studies were carried out in vitro with the livers of Japanese quail that had been fed from hatching on diets supplying their full requirements for vitamin D. 2. 25-Hydroxycholecalciferol was the major metabolite when liver homogenates of egg-laying female and oestrogen-treated quail of both sexes were incubated with [3H]cholecalciferol. 3. Very little 25-hydroxycholecalciferol was generated from liver homogenates of adult male and immature quail. Instead the cholecalciferol was converted into one or more compounds less polar than 25-hydroxycholecalciferol and into a number of highly polar metabolites, some of which were water-soluble. 4. Oestrogen not only stimulated the 25-hydroxylation of cholecalciferol but also protected both cholecalciferol and 25-hydroxycholecalciferol from degradation by the enzymic pathways active in immature and male birds. 5. These actions of oestrogen may be of physiological significance in relation to the high requirements of laying birds for 1,25-dihydroxycholecalciferol to support the intense metabolism of calcium associated with egg-shell calcification.

Aging↗
PubMed1978

Thermal transformation of cholecalciferol between 100--170 degrees C.

Cholecalciferol is transformed, irreversibly, to pyrocholecalciferol and isopyrocholecalciferol. The rate constant, as a function of temperature, for this transformation from the equilibrium mixture of cholecalciferol and precholecalciferol has been determined for temperatures between 100--170 degrees C and is slower than the precholecalciferol-cholecalciferol interconversion. The ratio of rates of production of pyro to isopyro derivatives is 2:1 throughout.

Chemical Phenomena↗
PubMed1978

Involvement of cholecalciferol metabolism in birds in the adaptation of calcium absorption to the needs during reproduction.

1. The metabolism of calcium and cholecalciferol in quail (Coturnix coturnix japonica) and chicken (Gallus domesticus) during maturation was correlated to gonadal activity and plasma oestrogen levels. 2. Birds with undeveloped ovaries (immature), developed ovaries but not laying (mature), and after laying 3-8 eggs (laying), were used in the first series. 3. Birds in which egg production had been arrested by Nicarbazin, were used in the second series. 4. Plasma 17 beta-oestradiol and calcium were elevated in the mature bird, with no further change in the laying bird. Kidney 25-hydroxycholecalciferol-1-hydroxylase and intestinal calcium-binding protein increased slightly in the mature bird, whereas they were grossly elevated in the laying bird. 5. Calcium and phosphorus absorption were markedly elevated in the laying bird. 6. No changes were noted in plasma 25-hydroxycholecalciferol, at any stage of maturation. 7. During the arrest of egg production by Nicarbazin, 17 beta-oestradiol level, calcium concentration of plasma, and medullary bone were maintained. Kidney 25-hydroxy-cholecalciferol-1-hydroxylase, intestinal calcium-binding protein and absorption of calcium were strikingly reduced. 8. The results suggest that changes in calcium absorption and cholecalciferol metabolism during maturation in birds are not directly affected by gonadal hormones; they appear to represent an adaptation to the increased calcium needs due to medullary bone formation and, more importantly, to the large losses of calcium imposed by shell formation.

Adaptation, Physiological↗
PubMed1975

The role of calcium binding protein in the mechanism of action of cholecalciferol (vitamin D3).

A role has been sought for the calcium binding protein (CaBP) which is synthesised de novo after giving cholecalciferol (CC, vitamin D3) to rachitic chicks. After homogenation of mucosal cells in sucrose media, the CaBP was found in the 78,000 X g supernatant. Therefore, the CaBP is either present in the cytoplasm or in some labile membrane structure, e.g. the microvilli, that is disrupted by homogenation. This intracellular CaBP may facilitate diffusion of Ca into intestinal cells. No secretion of CaBP into the lumen could be detected nor did excess CaBP placed in the lumen increase Ca absorption of rachitic chicks. The mitochondria of duodenal mucosal cells contained most of the Ca being translocated by the small intestine. CaBP caused release of Ca already present in mitochondria and diminished Ca uptake by mitochondria and it appreared to do this by increasing the rate of Ca flux across the mitochondrial membrane. This would explain the greater "turnover" of Ca in mucosal cells of cholecalciferol-treated chicks. These and previous findings have been used to propose a scheme for the effect of cholecalciferol on Ca transport from the small intestine.

Animals↗