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R Bouillon

Publications and source records attributed to R Bouillon.

At least 343 records · Page 19Linked to original sources
PubMed1984

Two direct (nonchromatographic) assays for 25-hydroxyvitamin D.

We describe direct, nonchromatographic assays for 25-hydroxyvitamin D3 in which we use either rat vitamin D-binding protein or rabbit antibodies to 25-hydroxyvitamin D3-3-hemisuccinate-bovine serum albumin as binding protein. Nonspecific interferences in serum could be eliminated by an appropriate extraction method or in obtaining data for the calibration curve, by using vitamin D-free human serum. The latter is prepared by affinity chromatography with use of immobilized antibodies against human vitamin D-binding protein. Values obtained by the direct assays and those obtained by two different chromatographic methods correlated well (r greater than 0.95). The direct competitive protein-binding assay overestimated the true 25-hydroxyvitamin D3 concentration by about 20%, but this percentage was constant from 5 to 600 micrograms/L. Overestimation by the direct radioimmunoassay was less than 10%. These two direct assays for 25-hydroxyvitamin D3 allow reliable, rapid, and simple screening for vitamin D deficiency or excess.

Acetates↗
PubMed1983

Radiochemical assays for vitamin D metabolites: technical possibilities and clinical applications.

Methods have been developed for the measurement of many, but not all, of the vitamin D metabolites. These methods are still laborious because of the necessity for extensive chromatographic purification but this may improve in the near future with the development of direct assays. By analogy with other steroid hormones, the production of better, and especially more specific, antibodies might be expected. In view of the numerous vitamin metabolites and isomers, chromatographic separation will however probably remain necessary for compounds present in low concentrations. The clinical usefulness of serum measurements of 25-OHD is now beyond doubt, especially since vitamin D deficiency is much more endemic than previously recognized. Measurement of 1,25-(OH)2D might also contribute to the clinical evaluation of disturbances of calcium metabolism but whether this also applies to other vitamin D metabolites awaits further research.

25-Hydroxyvitamin D 2↗
PubMed1982

Thyroid function in patients with hyperemesis gravidarum.

An increased free thyroxine (T4) index was observed in 73% of 33 consecutive pregnancies complicated by severe hyperemesis gravidarum. The free triiodothyronine (T3) index was increased in only four of 11 hyperthyroxinemic patients. In five hyperthyroxinemic patients tested, no increase in serum thyrotropin was observed after the injection of thyrotropin-releasing hormone (THR). Goiter, exophthalmos, or previous history of hyperthyroidism was absent in all patients. The thyroxinemia returned to normal in one to several weeks, whether or not it was treated with antithyroid drugs. The thyroid function during the period of hyperemesis had no influence on the subsequent rate of abortion or duration of pregnancy. A lower birth weight, however, was observed in children born to hyperthyroxinemic mothers. Hyperemesis gravidarum should be included in the differential diagnosis of elevations in free T4 index during pregnancy and included in the differential diagnosis of hyperthyroidism.

Abortion, Spontaneous↗
PubMed1982

Etiology of hypercalcemia in a patient with Addison's disease.

A case is reported of a hypercalcemic patient with primary Addison's disease. A combination of increased calcium input into the extracellular space and reduced calcium removal by the kidney accounted for the hypercalcemia. The mechanisms responsible for the reduction in calcium removal were decreased glomerular filtration and increased tubular calcium reabsorption. Both renal factors were secondary to volume depletion and improved rapidly during rehydration with saline infusion. The enhanced calcium mobilization was probably of skeletal origin. It persisted irrespective of volume status until hydrocortisone treatment was instituted. Serum 1,25-dihydroxyvitamin D3 levels were below 10 pg/ml, even after normalization of the glomerular filtration rate, but returned slowly to the normal range during corticosteroid substitution. Serum 25-hydroxyvitamin D3 and parathyroid hormone levels were within the normal range. Our case report therefore demonstrates that physiological amounts of glucocorticoids reduce bone resorption, normalize serum calcium, and restore the production of 1,25-dihydroxyvitamin D3.

Addison Disease↗
PubMed1982

Dynamics of growth hormone secretion in patients with osteoporosis and in patients with osteoarthrosis.

Basal plasma growth hormone levels as well as growth hormone levels during insulin -induced hypoglycemia have been studied in 19 cases with osteoporosis, in 34 patients with primary osteoarthrosis and in 19 control subjects. Women with primary osteoarthrosis had basal growth hormone levels significantly higher than control patients and patients with osteoporosis. The respective mean values and SE were: 4.9 +/- 0.8 vs. 1.9 +/- 0.8 and 1.3 +/- 0.2, p less than 0.025. During insulin-induced hypoglycemia the growth hormone levels rose to values which in osteoarthrotic women were significantly higher than in osteoporotics and in control subjects.

Aged↗
PubMed1981

Influence of the vitamin D-binding protein on the serum concentration of 1,25-dihydroxyvitamin D3. Significance of the free 1,25-dihydroxyvitamin D3 concentration.

The influence of the serum binding protein (DBP) for vitamin D and its metabolites on the concentration of its main ligands, 25-hydroxyvitamin D(3) (25-OHD(3)) and 1,25-dihydroxyvitamin D(3) (1,25-[OH](2)D(3)) was studied. The concentration of both 1,25-(OH)(2)D(3) and DBP in normal female subjects (45+/-14 ng/liter and 333+/-58 mg/liter, mean+/-SD, respectively; n = 58) increased during the intake of estro-progestogens (69+/-27 ng/liter and 488+/-90 mg/liter, respectively; n = 29), whereas the 25-OHD(3) concentration remained unchanged. A positive correlation was found between the concentrations of 1,25-(OH)(2)D(3) and DBP in these women. At the end of pregnancy, the total concentrations of 1,25-(OH)(2)D(3) (97+/-26 ng/liter, n = 40) and DBP (616+/-84 mg/liter) are both significantly higher than in nonpregnant females and paired cord serum samples (48+/-11 ng/liter and 266+/-41 mg/liter, respectively). A marked seasonal variation of 25-OHD(3) was observed in pregnant females and their infants, whereas in the same samples the concentrations of both DBP and 1,25-(OH)(2)D(3) remained constant throughout the year. The free 1,25-(OH)(2)D(3) index, calculated as the molar ratio of this steroid and DBP, remains normal in women taking estro-progestogens, however, and this might explain their normal intestinal calcium absorption despite a high total 1,25-(OH)(2)D(3) concentration. In pregnancy the free 1,25-(OH)(2)D(3) index remains normal up to 35 wk of gestation, but during the last weeks of gestation, the free 1,25-(OH)(2)D(3) index increases in both circulations. A highly significant correlation exists between the (total and free) 25-OHD(3) and 1,25-(OH)(2)D(3) concentrations in maternal and cord serum both at 35 and 40 wk of gestation.

Adult↗
PubMed1980

The isolation and characterization of the 25-hydroxyvitamin D-binding protein from chick serum.

The binding protein for 15-hydroxyvitamin D3 (25-OH-D3) was isolated from chick serum. The molecular weight was 60,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, without the existence of sub-units. Its sedimentation coefficient was 4.3 S. The isoelectric points of the major and minor components were 6.1 and 5.9, respectively. Addition of 25-hydroxyvitamin D3 causes an anodal shift in the isoelectric point of the two forms of the binding protein. Heating at 60 degrees C slowly destroys the binding protein but the addition of vitamin D metabolites increases its thermostability. The binding protein has probably a single binding site for all vitamin D metabolites and its association constant for 25-OH-D3 at 4 degrees C and pH 7.4 is 10(9) M-1. The same affinity is found for 24,25-dihydroxyvitamin D3 but 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 have a 3- and 10-fold lower affinity, respectively. The amino acid composition is very similar to that of the human and rat binding protein. The concentration of chick 25-hydroxyvitamin D3-binding protein was higher in egg-laying hens (10 microM) than in immature hens (4 microM) or immature or adult roosters (4 microM). Chick plasma contains virtually only a 4 S form of the 25-hydroxyvitamin D3-binding protein but partially hemolyzed chick serum also contains a 6 S form. Addition of pure actin to chick plasma or serum converts all 4 S form to the 6 S form. The serum 25-hydroxyvitamin D3-binding protein is thus heterogenous since it exists in two 4 S forms (with different pI) and a 6 S form (complexed with actin). No evidence was found for the existence of a separate vitamin D3-binding protein.

Amino Acids↗
PubMed1980

Vitamin D-binding protein (Gc-globulin) binds actin.

Actin, an ubiquitous highly conserved intracellular protein, and the serum vitamin D-binding protein (DBP) form tight 1:1 molar complexes in vitro. This interaction, which is not species-specific, explains the widespread occurrence of the 5-6 S protein responsible for the binding of 25-hydroxycholecalciferol in high speed supernatants of all nucleated tissues. Incubation of F-actin, the filamentous form of this protein, with DBP leads to depolymerization of the former. Actin, complexed with deoxyribonuclease I, retains its ability to bind DBP. Erythrocyte actin, prepared from red cell ghosts, also displays binding properties for DBP. The biological significance of this new interaction of actin is not yet understood.

Actins↗
PubMed1980

Lack of effect of the vitamin D status on the concentration of the vitamin D-binding protein in rat serum.

The influence of the vitamin D status on the concentration of the serum vitamin D-binding protein was studied. In normal rats the serum vitamin D-binding protein increases gradually from birth to adulthood; after puberty a higher concentration is found in male rats than in female rats. Rats fed a vitamin D-deficient diet containing a sufficient amount of calcium and phosphorus were found to have a normal DBP (binding protein for vitamin D and its hydroxylated metabolites) pattern indistinguishable from that of rats receiving the same diet but supplemented with a weekly injection of 500 microgram vitamin D3. Rats fed a vitamin D-deficient, low calcium, low phosphorus diet developed severe hypocalcemia and growth retardation, but their DBP pattern was not significantly different from that of rats fed the same diet but supplemented with a weekly injection of 500 microgram vitamin D3. The concentration of the transport protein for vitamin D was thus unrelated to the vitamin D status of the rat.

Aging↗
PubMed1980

Influence of thyroid function on the serum concentration of 1,25-dihydroxyvitamin D3.

The serum concentrations of parathyroid hormone, 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 were measured in patients with untreated thyroid disorders. The serum concentration of parathyroid hormone was decreased in hyperthyroidism [20 +/- 10 mU/liter, (mean +/- SD); n =23; P < 0.01] and increased in hypothyroidism (53 +/- 17 mU/liter; n = 12; P < 0.001) compared to that in normal subjects (26 +/- 9 mU/liter; n = 81). The concentration of 25-hydroxyvitamin D3 was not altered, but the concentration of 1,25-dihydroxyvitamin D3 was significantly lower in the serum of hyperthyroid patients (28 +/- 11 ng/liter) than in the serum of normal subjects (42 +/- 13 ng/liter). On the contrary, an increased concentration of 1,25-dihydroxyvitamin D3 was observed in the serum of hypothyroid patients (73 +/- 28 ng/liter; P < 0.001 vs. normal subjects). The abnormal serum concentrations of 1,25-dihydroxyvitamin D3 in thyroid disorders cannot be explained by differences in serum binding because the serum vitamin D-binding protein was unaltered in hyperthyroid subjects and only slightly increased (+17%) in hypothyroid subjects. These changes in the serum concentration of 1,25-dihydroxyvitamin D3 are compatible with previous data on altered intestinal calcium absorption in thyroid disorders.

Calcifediol↗
PubMed1980

A radioimmunoassay for 1,25-dihydroxycholecalciferol.

We describe a radioimmunoassay for 1,25-dihydroxycholecalciferol in human serum. We raised antisera in rabbits to 1,25-dihydroxycholecalciferol-3-hemisuccinate coupled to bovine serum albumin, and obtained sensitive, high-titer antibodies. These antibodies had a high affinity for 1,25-dihydroxycholecalciferol and cross reacted mainly with 25-hydroxycholecalciferol and 24,25-dihydroxycholecalciferol. Addition of 1 mL of normal rabbit serum per liter reduced this interference to 5 and 4%, respectively. However, these interfering steroids are present in large excess, so extensive purification of 1,25-dihydroxycholecalciferol from serum is necessary. The steroid was extracted with ethyl acetate/cyclohexane, purified on Sephadex LH-20, and then chromatographed on a column of silicic acid. The radioimmunoassay is sensitive to 5 pg/tube (3 ng/L of serum). The between-assay CV was 14%. The mean concentration of 1,25-dihydroxycholecalciferol in the serum of 54 healthy adults was 38 (SD 12) ng/L, with no sex-related difference. The assay was further validated by the finding of low or undetectable concentrations in patients with chronic renal failure and of increased concentrations in the serum of patients with primary hyperparathyroidism. In comparison with previously described methods, the major advantage of the present assay is the use of stable gamma-globulins, which are available in large amounts, as binding protein.

Adult↗