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1.
Yee S. Kim Stanley J. Birge Louis V. Avioli Ruth Miller 《Calcified tissue international》1987,41(4):218-222
Summary Rat osteogenic sarcoma cells have been used widely as a model system to study actions of 1,25(OH)2D3 and other hormones in osteoblastlike cells. However, some of the pleiotypic manifestations of hormones in these cells vary
greatly dependent upon the cell population density and other conditions of culture. Therefore, we have studied the effect
of cell density on the relationship between 1,25(OH)2D3 and the initial45Ca accumulation in ROS 17/2 cells in order to establish conditions suitable for studying the effect of 1,25(OH)2D3 on calcium fluxes in these cells. Cells were grown in the presence and absence of 1,25(OH)2D3 for 48 hours and then incubated for 4 min in the culture medium containing 0.5 μCi/ml of45CaCl2. In high population density cultures, 0.25–1.0 pg/ml of 1,25(OH)2D3 stimulated the intracellular accumulation of45Ca (cpm/mg protein), whereas 80 pg/ml or higher concentrations inhibited accumulation of45Ca. In low density cultures, concentrations less than 80 pg/ml had no effect, 80–120 pg/ml increased the intracellular accumulation,
and as much as 200 pg/ml failed to show the inhibitory effect. These results indicate that the ROS 17/2 cell responses to
1,25(OH)2D3 are biphasic—low concentrations stimulating and high concentrations inhibiting45Ca accumulation. The sensitivity of the cells to 1,25(OH)2D3 increases as the cell population density increases. These observations suggest that the culture density and dose-response
relationship must be carefully defined inin vitro studies utilizing osteogenic cell culture systems. 相似文献
2.
Stavros C. Manolagas Jean Abare Leonard J. Deftos 《Calcified tissue international》1984,36(1):153-157
Summary We have used cultured osteoblastlike rat osteogenic sarcoma cells (ROS 17/2) which have receptors for 1,25(OH)2D3 and for glucocorticoids, and have examined the modulation of the 1,25(OH)2D3 receptor by the potent glucocorticoid triamcinolone acetonide. We report that triamcinolone acetonide caused an increase
of the 1,25(OH)2D3 receptor concentration in these cells but it did not affect the affinity of the receptor to 1,25(OH)2D3; this phenomenon occurred in a dosedependent fashion for triamcinolone (10−9 to 10−7 M) with a maximum increase of 1,25(OH)2D3 receptor concentration of ⋍twofold. During the culture period, the 1,25(OH)2D3 receptor concentration was altered both in untreated as well as in triamcinolone-treated cells, being highest at the early
logarithmic phase and diminished progressively as cells approached confluence. However, throughout the culture period, the
1,25(OH)2D3 receptor concentration was higher in the triamcinolone-treated cells. 相似文献
3.
Summary The hormonal metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], exerts its biological effects by binding to a cytosolic receptor protein. Such a protein has been demonstrated in vitamin
D3 target organs including fetal rat calvariae and more recently in rat osteogenic sarcoma cells. In this study we have compared
the binding of 25-hydroxyvitamin D3 [25(OH)D3] and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] to that of 1,25-(OH)2D3 in fetal rat calvariae and osteogenic sarcoma (OS) cells. Sucrose density sedimentation, DNA-cellulose chromatography, and
intracellular uptake studies have been employed to evaluate these interactions.
In cytosol preparations from calvariae, [3H]-1,25(OH)2D3 bound to a 3.3S macromolecule and to a much greater extent to a 5.8S macromolecule while both [3H]25(OH)D3 and [3H]24,25(OH)2D3 bound to the 5.8S macromolecule. By incubating intact calvariae and OS cells with labeled metabolites and thus establishing
binding intracellularly prior to cell disruption, we have found that the 3.3S protein which has high specificity for 1,25(OH)2D3 occurs inside the cells; the 5.8S protein, however, does not occur inside the cells but is generated after cell disruption.
The [3H]-1,25(OH)2D3-receptor complex adsorbed to DNA-cellulose and was eluted from this affinity resin at 0.28M KCl. In contrast, [3H]25(OH)D3 and [3H]-24,25(OH)2D3 binding activity did not adsorb to DNA-cellulose. We conclude that, in contrast to the 3.3S protein, the 5.8S macromolecule
does not fulfill receptor criteria but is rather generated by the experimental manipulation of the bone cells. Our data suggest
that the vitamin D3 actions on bone are mediated only via the 3.3S receptor, and hence quantitative but not qualitative differences of the effects
of the various metabolites are feasible.
With technical assistance by M. Larsen, D. Meler, and M. LaFrance. 相似文献
4.
James A. Crowell Jr. Cary W. Cooper Svein U. Toverud Agna Boass 《Calcified tissue international》1984,36(1):320-326
Summary Studies presented here were designed to investigate further the basis for an impaired cAMP response to parathyroid hormone
(PTH) in osteoblastlike calvarial bone cells isolated from vitamin D-deficient rat pups. The goal was to perturb Ca, PTH,
and vitamin Din vivo in order to see which factors might be responsible for the impairedin vitro bone cell cAMP response. Pups either were parathyroidectomized (PTX) 3–5 days, implanted with osmotic minipumps delivering
high doses of PTH, given repeated, high doses of 1,25(OH)2D3, or were D-deficient (-D, i.e., born and suckled by D-deficient mothers). Osteoblastlike bone cells, isolated by sequential
enzyme digestion and centrifugation, were exposed to PTH for 5 min in the presence of a phosphodiesterase inhibitor. In bone
cells isolated from -D rat pups, both basal and PTH-induced cAMP accumulation were significantly lower than in +D bone cells.
Earlier, we had shown that two daily injections of -D pups with 50 ng 1,25(OH)2D3 restores this reduced bone cAMP response of -D pups toward normal. In the present study, neither basal nor PTH-induced bone
cell cAMP accumulation was affected by subjecting D-replete pups to PTX, PTH infusion, or repeated high doses of 1,25(OH)2D3 despite the fact that each treatment markedly changed serum Ca or serum immunoreactive PTH. The results indicate that the
impaired bone cell cAMP response seen in -D pups is not a direct result of chronic hypocalcemia and that the “heterologous
desensitization” seenin vitro with added 1,25(OH)2D3 could not be duplicated byin vivo treatment of +D pups with supraphysiologic doses of 1,25(OH)2D3. Finally the lack of alteration in the bone cell cAMP response to PTHin vitro after chronic PTH infusionin vivo fails to support the notion that the impaired response in -D bone cells can be explained entirely by “homologous desensitization”
induced by high circulating levels of PTH in the hypocalcemic, -D rat pup. 相似文献
5.
Summary The ability of 1,25(OH)2D3 and of 24,25(OH)2D3 to prevent or to heal rickets in chicks was evaluated by studies of plasma biochemistry, growth plate histology, bone morphometry
and microradiography, and bone mineralization. 1,25(OH)2D3 at a dose of 100 ng/day produced fewest abnormalities compared with vitamin D3-treated control chicks. Bone growth was slightly greater than vitamin D3-treated controls in chicks given a lower dose of this metabolite; the reverse was observed in chicks given a higher dose.
24,25(OH)2D3 was less effective than 1,25(OH)2D3 in preventing rickets even at doses as high as 400 ng/day. Treatment of rachitic chicks with doses of 24,25(OH)2D3 up to 300 ng/day produced no healing effect on the bone lesions, in marked contrast to the beneficial effects observed with
1,25(OH)2D3. 相似文献
6.
Summary The synthesis of matrix Gla protein (MGP) and bone Gla protein (BGP) have been shown to be mutually exclusive in all osteosarcoma
cell lines investigated. In the cell lines that produce the respective proteins, synthesis is stimulated by 1,25-dihydroxyvitamin
D3(1,25(OH)2D3) within the first several hours of hormone treatment. In the present studies we have investigated the effects of longer-term
treatment with 1,25(OH)2D3 in the ROS 17/2 cell line, a cell line that synthesizes BGP constitutively but does not synthesize MGP. In agreement with
earlier studies, the rate of BGP synthesis increases within 8 hours of hormone treatment, is maximal by 24 hours, and remains
at the maximal rate through 48 hours of 1,25(OH)2D3 treatment. The present study is the first to report that the rate of BGP secretion at times beyond 48 hours declines to that
of control cultures despite the continued administration of 1,25(OH)2D3, and that MGP synthesis is induced in ROS 17/2 cells by 48 hours of 1,25(OH)2D3 treatment. At this time, MGP mRNA could be detected by northern blot analysis and MGP secretion could be demonstrated by
radioimmunoassay of culture medium. Both the level of MGP message per unit total RNA and the rate of MGP secretion into culture
medium increased steadily between 2 and 6 days of 1,25(OH)2D3 treatment. The MGP synthesized by the 1,25(OH)2D3-treated ROS 17/2 cells was identical to that found in bone by northern blot analysis of message and by western blot analysis
of the media antigen. Halfmaximal induction of MGP synthesis was obtained with 0.3 nM 1,25(OH)2D3, a 60-fold higher dosage than was required for the half maximal stimulation of BGP synthesis in these cells. Treatment of
ROS 17/2 cells with 24,24-F21,25(OH)2D3 suggests that the observed difference in dose dependence is not due to an increased rate of hormone catabolism. 相似文献
7.
Summary Parathyroid hormone (PTH)-stimulated cyclic adenosine monophosphate (cAMP) in rat osteoblastlike (OB) cells has been shown
to be modulated by steroid hormones; glucocorticoids are known to increase the level, while the effects of 1,25(OH)2D3 are inhibitory. In the present study, we found that the PTH-stimulated cAMP responses are similar in neonatal mouse and fetal
rat OB cells. Dexamethasone (0.13–13nM) augmented PTH-stimulated cAMP in both species. Mouse cells showed a higher maximal
response to dexamethasone (100% increment) than rat cells (60–70% increment) with similar sensitivity to dexamethasone (ED50 ∼ 1.0 nm). On the other hand, 1,25(OH)2D3 decreased PTH-stimulated cAMP, but the effect required pharmacological levels of hormone; mouse cells responded at a lower
dose (1.3 nM) and were more sensitive than rat cells (responded at 13 nM) to 1,25(OH)2D3 treatment. Introduction of physiological concentrations of 1,25(OH)2D3 (0.013–1.3 nm) in addition to dexamethasone (13 nM) resulted in a synergistic enhancement of PTH-stimulated cAMP in rat cells.
In contrast, a dose-dependent antagonistic effect was observed in mouse cells. In summary, our findings demonstrate species
and concentration-dependent differences in hormonal responses to 1,25(OH)2D3 and a complex interplay among PTH, dexamethasone, and 1,25(OH)2D3. 相似文献
8.
Summary Cultured mouse kidney cells grown in serum-free medium were used to assess the metabolism of 25-hydroxyvitamin D3 in the presence of simulated metabolic acidosis. Kidney epithelial cells isolated from 4–6 week old mice were grown to confluence
in a defined serum-free medium at pH 7.4. The confluent monolayers were incubated with tritiated 25-hydroxyvitamin D3 for 6 hours, the samples were extracted, and vitamin D metabolites were separated and quantitated by high pressure liquid
chromatography (HPLC). The pH of the incubation medium was set at 6.9, 7.1, 7.4, or 7.7 by adjusting the bicarbonate concentration,
using chloride as the balancing anion at constant Pco2. When pH was altered at the beginning of the 6 hour assay, production of 1,25-dihydroxyvitamin D3 was the same at each pH. More prolonged pH perturbation for a total of 30 hours likewise had no influence on 1,25-dihydroxyvitamin
D3 production. These results confirm that intact mammalian kidney cells in serum-free culture possess an active 25-hydroxyvitamin
D3-1-hydroxylase and that the activity of the enzyme is unaffected by pH over the range 6.8–7.7. In experiments where acidosis
has been shown to alter 1,25-dihydroxyvitamin D3 production, the mechanism was probably indirect. 相似文献
9.
Summary The direct effect of 1,25(OH)2D3 upon osteoclast formation from precursor cells is still unknown. In the present experiments we have tested the effects of
1,25(OH)2D3 on the generation of osteoclastlike cells in cat bone marrow cultures. These cultures contain proliferating nonattached mononuclear
cells and precursor cells that subsequently attach to the culture flask surface and then fuse to form multinucleated osteoclastlike
cells. After 7 days of culture we separated the nonattached precursor cells from the attached cells and studied the effects
of 1,25(OH)2D3 (10−10 M–10−8 M) on multinucleated cell formation in these two cell populations. In cultures derived from the non-attached precursor cells,
7 days of treatment with 1,25(OH)2D3 (10−8 M) resulted in a 180% increase in the number of attached mononuclear cells and a 90% increase in the number of nuclei contained
within multinucleated cells. These effects were dose-dependent. 1,25(OH)2D3 did not have a consistent effect on the number of nonattached precursor cells. In cultures derived from attached cells, 7
days of treatment with 1,25(OH)2D3 (10−8 M) induced a 50% increase in the number of mononuclear attached cells and a 40% increase in the number of nuclei within polykaryons.
The most likely explanation for these results is that 1,25(OH)2D3 promotes the differentiation and subsequent adhesion of nonattached precursor cells, stimulates proliferation of attached
mononuclear precursor cells, and possibly stimulates fusion of these attached precursor cells. 相似文献
10.
Summary Vitamin D-deficient chicken embryos were obtained by feeding laying hens a diet in which 5 μg 1,25(OH)2D3/kg feed were substituted for the vitamin D3 supplement in the control diet. Hatchability, total Ca and inorganic P concentration in blood, and tibial ash/dry weight
ratio were determined in the vitamin D-deficient embryos and in embryos obtained from hens fed the control diet supplemented
with 1100 IU vitamin D3/kg feed. After 5 weeks on the substituted diet the hens laid eggs that showed decreased hatchability in spite of excellent
shell quality. All determinations in blood and bones were made on embryos of eggs laid after 6–12 weeks on the diets. On the
17th day of incubation the embryos derived from hens fed the substituted diet showed significant hypocalcemia and hyperphosphatemia
and a low tibial ash/dry weight ratio. Injection of 1,25(OH)2D3 3 days before killing corrected the hypocalcemia of the deficient embryos. Those chicks that managed to hatch had normal
levels of calcium and inorganic phosphate 1 day after hatching. These findings support previous suggestions by us and other
authors that vitamin D metabolites are required by the embryo in order to mobilize calcium from the shell, and decreased hatchability
in vitamin D-deficient embryos is related to a defect in calcium mobilization from the shell. While in previous studies a
decrease in hatchability was the only parameter used to judge D deficiency of the embryos in our present studies, the deficiency
is confirmed by demonstrating a deficit in mineral metabolism which is a more specific sign of D deficiency. 相似文献
11.
Daniel T. Baran Sook Won Lee O. D. Jo Louis V. Avioli 《Calcified tissue international》1982,34(1):165-168
Summary Classic (type I) renal tubular acidosis in children is attended by growth retardation and rickets, abnormalities that can
be corrected by alkali therapy alone. We have employed the NH4Cl-treated rachitic chick as a model to investigate vitamin D metabolism in the acidotic state. NH4Cl ingestion for 96 h was associated with a rise in serum calcium, a significant decrease in blood pH (7.42+0.08 vs 7.30±0.08,P<0.005), decreased [3H]1,25(OH)2D3 following [3H]25OHD D3 injections, and enhanced metabolic clearance of administered [3H]1,25(OH)2D3. The data collectively suggest that metabolic acidosis in the chick alters the production and degradation of 1,25(OH)2D3. 相似文献
12.
Socorro Vargas Roger Bouillon Hugo Van Baelen Dr. Lawrence G. Raisz 《Calcified tissue international》1990,47(3):164-168
Summary Vitamin D and its metabolites are tightly bound to the serum vitamin D-binding protein (DBP) and only the free hormone is
considered to be physiologically active. On the other hand, DBP could interact with cell membranes and even favor its intracellular
entry. The present study was undertaken to examine the effects of DBP on bone resorption stimulated by 1,25-dihydroxyvitamin
D3 [1,25(OH)2D3]. Forelimb bones from 19-day-old fetal rats were cultured for 5 days in the presence of purified human or rat serum albumin
(hSAP or rSAP) and 1,25(OH)2D3, with or without human or rat DBP (hDBP or rDBP). Bone resorption was assessed by measuring the release of previously incorporated45Ca. We found that the resorptive response to 1,25(OH)2D3 was minimally altered by hDBP (5 μM). The minimal effects of hDBP on 1,25(OH)2D3 activity on rat bones might be explained by a 6-fold lower affinity of hDBP (1.1×107 M−1) than rDBP (5.9×107 M−1) for 1,25(OH)2D3 or by species differences in cellular recognition of DBP. In a homologous rat system, however, rDBP at low (0.5 μM) or physiological
(5 μM) concentration significantly decreased 1,25(OH)2D3-induced bone resorption. These data therefore support the hypothesis that free rather than DBP-bound 1,25(OH)2D3 is physiologically important. 相似文献
13.
Marcos Rothstein Klaus Olgaard Mario Arbelaez Delmar Finco Saulo Klahr Eduardo Slatopolsky M.D. 《Calcified tissue international》1983,35(1):449-454
Summary The role of 24,25(OH)2D3 on parathyroid gland function remains controversial. The present studies were performedin vitro using (a) dispersed normal bovine parathyroid cells (bPTC) and (b) dispersed canine PTC (cPTC) prepared from glands of normal
dogs, dogs with chronic renal failure (CRF), and dogs with CRF treated with 24,25(OH)2D3, 2.5 μg orally every day for more than 6 months. Bovine parathyroid cells were incubated for up to 180 min at 0.5, 1.0, and
3.0 mM external calcium in the presence or absence of 24,25(OH)2D3 (100 or 1000 nM). Similar experiments were conducted with cells incubated for 24 h in the presence of either the ethanol
vehicle or 24,25(OH)2D3 (1000 nM). Parathyroid hormone secretion, measured in the supernatant by both C-terminal and N-terminal assays, did not show
any differences between control and experimental groups at any time interval. Canine parathyroid cells obtained from uremic
animals showed an average threefold increase in the total amount of PTH secreted, on a per cell basis over 180 min at 0.5
mM Ca2+, when compared with normal controls. However, there was no significant difference in PTH secretion at any level of calcium
concentration between the cells obtained from parathyroid glands of CRF dogs and 24,25(OH)2D3-treated CRF dogs. Acute exposure to 24,25(OH)2D3 (1000 nM)in vitro of the cells obtained from the glands of CRF dogs also had no effect on PTH secretion. We conclude that 24,25(OH)2D3 has no direct effect on PTH secretion from dispersed parathyroid cells of either normal or uremic animals. 相似文献
14.
15.
Summary Binding of [3H] 1,25 (OH)2D3 and effects of 1,25 (OH)2D3 on cell ultrastructure were evaluated in vascular smooth muscle cells (VSMC) primary cultures (aortic media). Specific reversible
binding of [3H] 1,25 (OH)2D3 by a 3.5 S macromolecule with DNA binding, KD 6.2×10−10M and Nmax 16 fmol/mg protein was demonstrated. Incubation of VSMC with 10−8 M 1,25 (OH)2D3, but not 25 (OH)D3, in the presence of 10% FCS for up to three weeks caused rapid reversible appearance in the cytoplasm of membrane-bounded
electron-dense lysosomal particles which on electronspectroscopic imaging contained Ca and Pi. VSMC are targets for vitamin
D. 相似文献
16.
Janine Fritsch Brigitte Grosse Michèle Lieberherr Sonia Balsan 《Calcified tissue international》1985,37(6):639-645
Summary Osteoblastic cells were isolated from periosteum-stripped parietal bones of neonatal rat calvaria, seeded at low density (5,000
cells/35 mm of Falcon dish), and cultured for 6 days in BGJ medium supplemented with 20% of vitamin D-depleted FCS or vitamin
D and calcium-depleted FCS, with daily addition of 1,25 dihydroxyvitamin D3 (10−9 M) or 24,25-dihydroxyvitamin D3 (10−9 M). Plating efficiency, clonal growth (number and size distribution of the colonies formed), and the alkaline phosphatase
phenotype were evaluated on days 2 and 6 of culture. (1) Culture for 6 days in media not supplemented with 1,25(OH)2D3 led to a significant (P<0.001) loss of the alkaline phosphatase phenotype of the osteoblastic cells; the loss was greater in proliferating cells
than in nonproliferating ones and occurred in both 0.12 mM or 1.1 mM ionized calcium concentrations. (2) Daily addition of
1,25(OH)2D3 (10−9 M) but not 24,25(OH)2D3 maintained the basal percentage of Alk Pase positive cell units in nonproliferating cells and significantly reduced the loss
of this phenotype in proliferating colonies. (3) This effect did not stem from an action of the hormone on cell growth. 1,25(OH)2D3 was also found to enhance the adhesiveness of the seeded osteoblasts, irrespective of the medium calcium concentration. 相似文献
17.
G. G. Langston L. D. Swain Z. Schwartz F. Del Toro R. Gomez Barbara D. Boyan 《Calcified tissue international》1990,47(4):230-236
Summary Vitamin D3 metabolites have been shown to affect proliferation, differentiation, and maturation of cartilage cells. Previous studies
have shown that growth zone chondrocytes respond primarily to 1,25(OH)2D3 whereas resting zone chondrocytes respond primarily to 24,25(OH)2D3. To examine the role of calcium in the mechanism of hormone action, this study examined the effects of the Ca ionophore A23187,
1,25(OH)2D3, and 24,25(OH)2D3 on Ca influx and efflux in growth zone chondrocytes and resting zone chondrocytes derived from the costochondral junction
of 125 g rats. Influex was measured as incorporation of45Ca. Efflux was measured as release of45Ca from prelabeled cultures into fresh media. The pattern of45Ca influx in unstimulated (control) cells over the incubation period was different in the two chondrocyte populations, whereas
the pattern of efflux was comparable. A23187 induced a rapid influx of45Ca in both types of chondrocytes which peaked by 3 minutes and was over by 6 minutes. Influx was greatest in the growth zone
chondrocytes. Addition of 10−8–10−9 M 1,25(OH)2D3 to growth zone chondrocyte cultures results in a dose-dependent increase in45Ca influx after 15 minutes. Efflux was stimulated by these concentrations of hormone throughout the incubation period. Addition
of 10−6–10−7 M 24,25(OH)2D3 to resting zone chondrocytes resulted in an inhibition in ion efflux between 1 and 6 minutes, with no effect on influx during
this period. Efflux returned to control values between 6 and 15 minutes.45Ca influx was inhibited by these concentrations of hormone from 15 to 30 minutes. These studies demonstrate that changes in
Ca influx and efflux are metabolite specific and may be a mechanism by which vitamin D metabolites directly regulated chondrocytes
in culture. 相似文献
18.
Dr. J. R. M'Buyamba-Kabangu R. Fagard P. Lijnen R. Bouillon W. Lissens A. Amery 《Calcified tissue international》1987,41(2):70-74
Summary The serum and urinary calcium, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and parathyroid hormone (PTH) were studied in healthy black and white males living in Belgium, and the results were compared
to data in blacks of similar age living in Za?re. Dietary calcium and vitamin D were estimated in a subsample of blacks and
whites examined in Belgium. Compared to whites (9.51±0.28 mg%) serum calcium was somewhat lower in blacks (9.26±0.27 mg% in
Belgium; 9.19±0.48 mg% in Za?re). The 24 hour urinary calcium excretion averaged 215.0±16.7 mg% in whites and was higher (P<0.05 or less) than in blacks (115±71 mg% in Belgium; 36±33 mg% in Za?re). The serum 25OHD levels were similar in whites and
blacks evaluated in Za?re, both being higher (P<0.05 or less) than in blacks living in Belgium. In the latter blacks, an inverse correlation was observed between the 25OHD
level and the duration of the stay in a temperate climate. Parathyroid hormone levels were slightly higher in blacks living
in Belgium than in the other two groups of subjects. The serum levels of 1,25(OH)2D3 and human vitamin D-binding protein were similar in the three groups of subjects. Dietary calcium averaged 541±152 mg/day
in blacks and was significantly (P<0.001) less than in whites (1,203±508 mg/day), whereas no significant difference was observed in dietary vitamin D intake
between blacks and whites. It is concluded that calcium intake is low in blacks but stimulation of parathyroid hormone and
1,25(OH)2D3 required to achieve normocalcemia does not occur. 相似文献
19.
Dr. Dalia Sömjen Alvin M. Kaye Gideon A. Rodan Itzhak Binderman 《Calcified tissue international》1985,37(6):635-638
Summary We have previously shown that both parathyroid hormone (PTH) and prostaglandin E2 (PGE2) stimulate the activity of creatine kinase BB (CKBB) in rat bone cells in culture. Therefore, morphologically distinct rat
osteogenic sarcoma cells in culture were tested for stimulation of CKBB activity by hormones that regulate skeletal tissues.
PTH stimulated CKBB in the osteoblast-like clone ROS 17/2; 1α,25(OH)2D3 inhibited this activity while PGE2, CT and 24R,25(OH)2D3 had no significant effect. PGE2 stimulated CKBB activity in the fibroblast-like clone ROS 24/1, which was unresponsive to PTH, CT and Vitamin D metabolites.
24R,25(OH)2D3 as well as PGE2 (but not PTH, CT or 1α25(OH)2D3) stimulated CKBB in clone ROS 25/1, suggesting that this fibroblast-like clone has some chondroblast-like character. Both
PTH and PGE2 stimulated the brain type isoenzyme of CK (CKBB), although the osteogenic sarcoma cell clones contain a significant proportion
of the muscle type of CK (CKMM). Thus, increased CKBB activity can serve as an additional characteristic marker for the action
of steroid and polypeptide hormones and for prostaglandins. 相似文献
20.
The effects of retinoic acid (RA), and calcitriol are mediated by specific nuclear receptors (RARs and VDR, respectively). Induction of RAR and VDR responsive elements in target genes requires a cofactor, the retinoid-X-receptor (RXR), with its ligand 9-cis RA. We have previously demonstrated the expression of RARs and RXRs in osteoblasts, and herein investigated the effects of the retinoids all-trans RA and 9-cis RA alone and combined with calcitriol on bone resorption in vitro, measured by 45Ca-release from prelabeled neonatal mouse calvarial bones. All-trans RA and 9-cis RA were powerful stimulators of bone resorption and essentially equipotent. At threshold concentrations (1 nM) both 9-cis RA and at-RA markedly inhibited the resorption induced by calcitriol (1 pM). The findings are compatible with a physiological role for retinoids in bone metabolism. 相似文献