ISSN:0884-0431    

DOI:10.1002/jbmr.5650110802

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110803

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractIn an effort to design and select potent parathyroid hormone (PTH) antagonists suitable for clinical utility, a PTH analog was evaluated in vivo in an animal model to assess its properties in preparation for human studies. The previously described PTH antagonist, [Nle8,18, D‐Trp12, Tyr34]bPTH(7–34)NH2, which is highly active in vitro, was documented in these studies to be an effective antagonist of the PTH‐stimulated calcemic response in vivo. In thyroparathyroidectomized (TPTX) rats, the efficacy of the antagonist was demonstrated to be dose‐dependent. Inhibition was demonstrated when intravenous administration of antagonist started 1 h prior to coinfusion with the PTH agonist [Nle8,18,Tyr34]bPTH(1–34)NH2. Maximal inhibition by antagonist (an 84% decline in serum calcium levels compared with agonist alone) of the calcemic response was observed when a 200‐fold molar excess of antagonist (12 nmol/h) was administered. At dose ratios of antagonist:agonist as low as 10:1, a 40–50% inhibition of PTH‐stimulated calcemic response is evident, provided a longer (2 h) lead time for antagonist infusion is allowed. Based on these and related studies, the antagonist [Nle8,18,D‐Trp12,Tyr34]bPTH(7–34) NH2has displayed sufficient potency to obtain approval from the appropriate institutional and regulatory agencies for clinical trials in hypercalcemic states of parathyro

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110804

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have evaluated the signaling pathways activated by parathyroid hormone (PTH) in SaOS2human osteoblast‐like cells correlating with induction of thec‐fosproto‐oncogene. Human PTH (1–34) (hPTH[1–34]) and hPTH(1–34) Nle8,18Tyr34induced the expression ofc‐fosmRNA in quiescent SaOS2cells in a concentration‐dependent manner. N‐terminal truncations of hPTH(1–34) that fail to activate protein kinase A (PKA) also abolishedc‐fosmRNA induction. In gel retardation assays hPTH(1–34) led to a change in the mobility of specific, cyclic adenosine monophosphate (cAMP) response element binding protein (CREB)‐containing protein‐DNA complexes identical to that caused by other activators of PKA. The appearance of this altered mobility complex correlated temporally with the induction ofc‐fosmRNA. Using ac‐fosserum response element probe, a slowed protein DNA complex appeared upon serum, epidermal growth factor, and basic fibroblast growth factor treatment. This slowed complex reflects phosphorylation of the transcription factor ternary complex factor (TCF) mediated via activation of the mitogen‐activated protein (MAP) kinase pathway. The MAP kinase cascade is also activated by protein kinase C (PKC), and treatment with phorbol ester led to the induced TCF shift. In contrast, PTH did not produce this shift, ruling out PTH activation ofc‐fosvia PKC and the MAP kinase signaling cascade. Further evidence for this was the lack of effect of the highly selective PKC inhibitor CGP 41251 onc‐fosinduction by hPTH(1–34). The janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling cascade targets thev‐sis‐inducible element in thec‐fospromoter via the induced binding of STATs. Interferon γ rapidly induced STAT binding in SaOS2cells, unlike PTH. Thus, PTH induction ofc‐fostranscription appears to occur principally through activation of PKA that then target

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110805

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractThe role of hormone secretion and hormone clearance in the differential control of circulating levels of intact (I‐) and carboxy‐terminal (C‐) immunoreactive parathyroid hormone (iPTH) was evaluated in 18 pentobarbital‐anesthetized dogs. Catheters were installed in the aorta, left renal, and hepatic veins for sampling. Hepatic and renal blood flows were calculated from sulfobromophtalein (BSP) and p‐aminohippuric acid (PAH) extraction and clearance. I‐ and C‐iPTH were measured during a 1 h of infusion of CaCl2or Na2EDTA. High‐performance liquid chromatography (HPLC) profiles of I‐ and C‐iPTH in and out of the liver and kidney were also obtained. Data on two dogs (one CaCl2and one Na2EDTA infusion) were pooled for the analysis of one parathyroid function using a four‐parameter mathematical model. Results obtained in the basal state and during analysis of the parathyroid function were also compared with those of 24 awakened dogs. Results are means ± SD. Anesthetized dogs had lower levels of Ca2+(1.29 ± 0.03 vs. 1.34 ± 0.04 mmol/l;p<0.001) and higher levels of I‐ (11.5 ± 5.7 vs. 3.0 ± 1.9 pmol/l,p<0.001) and C‐iPTH (52 ± 20.9 vs. 22.8 ± 10.5 pmol/l;p<0.001) than awakened dogs. Their stimulated (S) and nonsuppressible (NS) I‐iPTH levels were increased 2‐ and 4‐fold, respectively, while similar C‐iPTH levels rose only 1.35‐ and 1.75‐fold; this caused their S (4.4 ± 0.7 vs. 6.8 ± 1.9;p<0.001) and NS (24.6 ± 11.8 vs. 49.8 ± 27.5;p<0.05) C‐iPTH/I‐iPTH ratios to decrease. This was not explained by different renal clearance rates of I‐ and C‐iPTH since both were similar at ∼10 ml/kg/minute and unaffected by Ca2+concentration. Clearance of all I‐ and C‐iPTH HPLC molecular forms by the kidney appeared equal. A 50% decrease in the hepatic clearance of I‐iPTH to ∼12 ml/kg/minute in pentobarbital‐anesthetized dogs, related to a lower hepatic blood flow, explained the higher levels of S and NS I‐iPTH in these animals. I‐iPTH hepatic clearance was unaffected by Ca2+concentration. C‐iPTH hepatic clearance was much lower at ∼5 ml/kg/minute, abolished by hypercalcemia, and reduced by the influence of anesthesia on hepatic blood flow. This also explained the higher S C‐iPTH levels in anesthetized animals. I‐PTH(1–84) detected by the C‐iPTH assay explained only 37.6% of the hepatic C‐iPTH clearance in hypocalcemia and 73.3% in hypercalcemia. Overall, our results indicate that total C‐iPTH clearance is about 40.2% that of I‐iPTH in hypocalcemia and 41.3% in hypercalcemia. This would only explain a 2.4‐ to 2.5‐fold difference in circulating levels of I‐ and C‐iPTH if secretion rates were equal; the larger difference obser

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110806

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractThe present investigation was conducted to examine the effects of parathyroid hormone (PTH) and parathyroid hormone related peptide (PTHrP) on renal calbindin‐D28k in rats. Four groups of studies were performed: (1) parathyroidectomy (PTX) or a sham operation followed by infusion of 1,25‐dihydroxyvitamin D (1,25[OH]2D) or vehicle; (2) infusions of PTH(1‐34), PTH(1‐84), 1,25(OH)2D, or vehicle; (3) infusion of PTHrP(1‐34), PTHrP (1‐86), PTH(1‐34), or vehicle; and (4) injections of calcium or vehicle. PTX reduced renal calbindin‐D28k levels even when plasma concentrations of 1,25(OH)2D were kept constant by infusion of 1,25(OH)2D. Infusions of PTH(1‐34), PTH(1‐84), and 1,25(OH)2D all increased renal calbindin‐D28k and plasma calcium, whereas PTHrP(1‐34) and PTHrP(1‐86) increased renal calbindin‐D28k before an increase of plasma calcium took place. Hypercalcemia induced by the injection of calcium did not affect the levels of renal calbindin‐D28k. The present data suggest that PTH and PTHrP exert a direct effect on renal calbindin‐D28k, which is not mediated by c

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110807

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractThe influence of growth hormone administration on cancellous and cortical bone of the vertebral body in 2‐year‐old male rats has been investigated. All rats were injected for 80 days, then killed. Controls were given saline, and three recombinant human growth hormone (rhGH) injected groups were given either rhGH (2.7 mg/kg/day) for the first 20 or 40 days, followed by saline injection, or rhGH for all 80 days. Tetracycline labeling was performed on days 41 and 69. In all groups given rhGH, an increase in the cortical bone volume was found. In the rhGH 40‐day group, single labeling corresponding to injection on day 41 was seen all around the anterior surface of the vertebral body wall (toward the abdominal cavity). In the rhGH 80‐day group, double labeling was seen all around the anterior surface of the vertebral body, and a substantial increase in the mineralizing surface/total surface, mineral apposition rate, and mineralized bone formation rate was found. In the cortical bone of the anterior wall, cavities had developed in the rhGH 40‐ and 80‐day groups. In the cancellous bone, no differences in bone volume, bone volume/total volume, or bone surface/bone volume were seen, but in the middle part of the vertebral body a decrease in the mineralizing surface/total surface was found in the rhGH 80‐day group. The height of the vertebral body was not influenced by rhGH administration, whereas the transversal and midsaggital diameters were increased in the rhGH 80‐day group. The compressive mechanical strength of the vertebral body specimens was increased in the rhGH 80‐day group, and this increase most likely could be explained by formation and deposition

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110808

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractLongitudinal growth is a result of proliferation and differentiation of chondrocytes in the growth plate. Growth hormone (GH) stimulates longitudinal growth, and GH receptors have been shown on growth plate chondrocytes, but the effects of GH on chondrocytes of different cell layers are not clear. To study the effect of GH on chondrocyte activity, in situ biochemical techniques were used to measure enzyme activities, which are associated with cell differentiation (alkaline phosphatase [ALP]) and osteoclast activity (tartrate‐resistant acid phosphatase [TRAP]), within single cells of the growth plate. Uptake of bromodeoxyuridine (BrdU) was used as a parameter for proliferative activity. In addition, glucose‐6‐phosphate dehydrogenase (G6PD) was measured since increased proliferation has been associated with increased G6PD activity. The role of GH was studied in a model of isolated GH deficiency (dwarf rat) and complete pituitary deficiency (hypophysectomized rat). Groups of GH‐deficient dwarf rats were infused with recombinant human GH in either a continuous or a pulsatile manner, since the pattern of GH secretion is an important regulator of growth in the rat. After 7 days, G6PD activity in proliferative chondrocytes and TRAP activity in osteoclasts was increased, while ALP activity in hypertrophic chondrocytes was decreased. GH not only increased the number of chondrocytes that incorporated BrdU but also the total number of chondrocytes in the proliferative zone; therefore, its ratio, the labeling index (an indicator of proliferative rate), was not increased. The widths of the proliferative and hypertrophic zones were increased by both patterns of GH administration. The width of the resting zone was unaffected by continuous GH but decreased by pulsatile GH. ALP and TRAP activities were, respectively, higher and lower in hypophysectomized rats compared with the GH‐deficient animals. Hypophysectomized rats had smaller growth plates than dwarf rats with a disproportionally wide resting zone, which, like BrdU uptake, was not affected by GH. GH treatment resulted in increased TRAP and decreased ALP activity. These results indicate that GH stimulates the commitment of chondrocytes within the resting/germinal layer to a proliferative phenotype (as opposed to stimulating the rate of chondrocyte proliferation) but only in the presence of other pituitary hormones. Furthermore, this study shows that enzyme activities within single chondrocytes and osteoclasts are GH‐sensitive. The extent to which these effects are direct or mediated by systemic or local growth factors remains to b

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110809

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to evaluate the usefulness in osteoporosis of a new ultrasound imaging device able to create a parametric image of broadband ultrasound attenuation (BUA) at the os calcis. Three regions of interest were located in the great tuberosity of the os calcis. Precision was evaluated in 37 patients. Calcaneal bone mineral density (BMD) and BUA were compared in 33 patients. In 236 patients (including 77 with osteoporotic fractures), BUA and lumbar and femoral BMD measurements were performed. The measurements were compared using correlation coefficients. Their clinical value was estimated by comparisons of the results between patients with fractures and age‐matched controls, using comparisons of the means, areas under the ROC curves, and logistic regression. Precision was in a 1.4‐3.3% range. Local BUA and BMD were highly correlated (r= 0.88). Significant correlations were found between BUA and lumbar (r= 0.56) and femur (r= 0.66) BMD. In multiple regression, years since menopause and weight were significant predictors of BUA. Patients with fractures had lower BUA and BMD than age‐matched controls. BUA showed the largest difference between the two populations (13‐16%). Areas under the ROC curves were similar for BUA and BMD. Logistic regression after adjustment for confounding factors showed that BUA discriminated between fracture and nonfracture subjects. Broadband ultrasound attenuation imaging improves the reproducibility of ultrasound measurements. It may be useful in osteoporosis, due to its good discriminatin

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110810

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY

摘要:

AbstractAlthough the effects of interleukin‐1 (IL‐1) and interleukin‐6 (IL‐6) on articular cartilage chondrocytes have been reported, little is known concerning the effects of these cytokines on growth plate chondrocytes. In this study, we examined the effect of IL‐1α, IL‐1β, and IL‐6 on growth plate chondrocyte proliferation, differentiation, and matrix production as a function of cell maturation and examined the ability of these cells to produce IL‐1α and IL‐1β. Confluent fourth passage cultures of rat costochondral resting zone and growth zone chondrocytes were treated with 0–100 ng/ml of IL‐1α, IL‐1β, or IL‐6 for 24 h and then assayed for [3H]‐thymidine incorporation, alkaline phosphatase specific activity, [35S]‐sulfate incorporation, and percent collagen production. Neutralizing polyclonal antibodies were used to confirm the specificity of response to each cytokine. Treatment of resting zone cells with IL‐1α produced a significant, dose‐dependent decrease in [3H]‐thymidine incorporation, while similarly treated growth zone cells were unaffected by treatment with this cytokine. IL‐1α also stimulated alkaline phosphatase specific activity and inhibited [35S]‐sulfate incorporation by resting zone chondrocytes, but had no affect on growth zone chondrocytes. When collagen production was examined, it was observed that IL‐1α had a stimulatory affect on growth zone cells but no affect on resting zone cells. When the effect of IL‐1β was examined, it was observed that this cytokine inhibited [3H]‐thymidine incorporation by resting zone cells and stimulated isotope incorporation in growth zone cells. IL‐1β also stimulated alkaline phosphatase specific activity and inhibited [35S]‐sulfate incorporation by resting zone chondrocytes but had no affect on growth zone chondrocytes. In contrast to IL‐1α, IL‐1β stimulated collagen production by resting zone cells but not growth zone cells. IL‐6 had no affect on any of the parameters measured in either cell type. When cytokine production was measured, it was found that IL‐1α was produced by both cell types, while IL‐1β was produced only by resting zone cells. Resting zone cells secreted both IL‐1α and IL‐1β into the media, but 75% of the total cytokine produced by these cells was retained in the cell layer. In contrast, growth zone cells did not secrete measurable IL‐1α into the media. These results suggest that IL‐1α and IL‐1β target resting zone cells, inducing them to differentiate and acquire a phenotype characteristic of the more mature growth zone cells. Moreover, resting zone chondrocytes produce both IL‐1α

ISSN:0884-0431    

DOI:10.1002/jbmr.5650110811

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1996

数据来源: WILEY