Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:7440-70-2 (calcium)
 333,191 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypercalcemia is a frequent complication of cancer. Recently, parathyroid hormone-related protein has been isolated from tumors associated with this syndrome. In the present study, the effects of tumor-derived hypercalcemic factor and bovine parathyroid hormone (PTH) on bone were compared in an organ culture system using calvarial bones from newborn mice. Mouse calvaria were incubated for 72 h with control medium or media containing 0.15 mg/m tumor extract (TE) or 2 x 10(-9) M PTH. Bone resorption, as assessed by the amount of calcium released into the medium and the number of osteoclasts counted on light microscopy, was increased by both PTH and TE. On electron microscopy, areas for cytoplasm, ruffled border and clear zone were statistically increased in PTH- and TE-treated calvaria as compared to control. These values were not significantly different between PTH- and TE-treated calvaria. The study therefore demonstrates that the ultrastructural changes in osteoclasts induced by the hypercalcemia-producing TE are similar to those induced by PTH.
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PMID:Effects of hypercalcemia-producing tumor extract and parathyroid hormone on osteoclast ultrastructure. 231 31

Studies on humoral hypercalcemia of malignancy have shown that tumors produce a protein that acts through the parathyroid hormone (PTH) receptor but is immunologically distinct from PTH. We have recently purified and cloned a parathyroid hormone-related protein (PTHrP) from a human lung cancer cell line. Full length cDNA clones were isolated and found to encode a prepropeptide of 36 amino acids and a mature protein of 141 amino acids. Eight of the first 13 amino terminal residues are identical with human PTH, although antisera directed at the amino terminus of PTHrP do not recognize PTH. A 34-amino acid synthetic peptide, PTHrP(1-34), was several times more potent than bovine or human PTH(1-34) in bioassays promoting the formation of cAMP and plasminogen activity in osteogenic sarcoma cells and activation of adenylate cyclase in chick kidney membranes. PTHrP(1-34) was also more potent than PTH(1-34) in stimulating cAMP and phosphate excretion and reducing calcium excretion in the isolated perfused rat kidney. PTHrP has been consistently demonstrated by immunohistochemistry in squamous cell carcinomas and in keratinocytes present in normal skin, but not in normal or hyperplastic parathyroid tissues or other tumors. PTHrP-like activity has been extracted from ovine placenta and fetal parathyroid tissue, suggesting that PTHrP may play a role in fetal calcium homeostasis.
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PMID:Humoral hypercalcemia of malignancy. 233 5

A 54-yr-old man with a left adrenal pheochromocytoma showed mild hypercalcemia and elevated nephrogenous cAMP. Serum levels of PTH and 1,25-dihydroxyvitamin D3 were not elevated. Postoperatively, serum calcium and nephrogenous cAMP declined to normal ranges. Pathologically, the tumor was a benign pheochromocytoma. The clinical findings resembled those of humoral hypercalcemia of malignancy (HHM), and PTH-related protein (PTHrP) immunoreactivity was detected in the tumor extract at a concentration of 80.7 pmol/g wet wt, which is high compared to levels in malignant tumors causing HHM. Production of PTHrP was further confirmed by the demonstration of PTHrP mRNA with Northern blot hybridization analysis. Gel filtration of the extract revealed the presence of at least two different molecules with both immunological and biological activities. One of the peaks appeared close to PTHrP-(1-34), and the other between cytochrome-c and BSA. The latter showed a higher bioactivity to immunoreactivity ratio. These data indicate the multiplicity of PTHrP molecules in pheochromocytoma and support the idea that PTHrP produced by pheochromocytoma causes hypercalcemia in a similar fashion as HHM.
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PMID:A case of pheochromocytoma producing parathyroid hormone-related protein and presenting with hypercalcemia. 234 92

The Rice H500 rat Leydig cell tumor is a well characterized model of humoral hypercalcemia of malignancy (HHM). Circulating concentrations of PTH-related protein (PTHRP) have not been reported in this or any other animal model of HHM. Taking advantage of the marked N-terminal amino acid homology between rodent and human PTHRPs, we have adapted a sensitive two-site immunoradiometric assay developed for measurement of human PTHRP for use in measuring rat PTHRP. Circulating calcium and PTHRP concentrations were serially measured after sc passage of the Leydig cell tumor in rats. Significant hypercalcemia and elevation of PTHRP occurred on day 9 after tumor inoculation. When grouped by tumor size, both plasma calcium and PTHRP levels were significantly elevated in animals with tumor burdens greater than 10 cc. The PTHRP concentration was strongly correlated with both serum calcium (r = 0.88) and tumor size (r = 0.80). Circulating rat PTHRP averaged 12.8 pM on day 9 and 27.5 pM on day 10 or 11. PTHRP was undetectable in the plasma of 19 control rats. In 3 rats, plasma calcium returned to normal, and PTHRP became undetectable within 24 h after tumor excision. Rat milk displayed a PTHRP concentration of 2000 pM, while acid-urea extract of the rat tumor contained 0.32 pmol/mg protein. Dilutions of rat plasma, milk, and tumor extract displayed response curves that were parallel to the human PTHRP-(1-74) standard in the assay. This two-site immunoradiometric assay is a sensitive and easily performed means of measuring rat PTHRP. It should be useful in studying this animal model of HHM and the function of PTHRP in normal tissues.
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PMID:Measurement of circulating parathyroid hormone-related protein in rats with humoral hypercalcemia of malignancy using a two-site immunoradiometric assay. 238 60

We investigated the possible involvement of parathyroid hormone-related protein (PTHrP) in 2 cases of metastatic pancreatic neuro-endocrine tumors associated with severe hypercalcemia. Both patients displayed biochemical alterations in renal tubular reabsorption of calcium and phosphate, as well as in urinary cAMP excretion, similar to those encountered in primary hyperparathyroidism, although plasma levels of parathyroid hormone were within the normal range. Tumor protein extracts stimulated cAMP production, which was inhibited by the PTH-antagonist (8,18 Nle, 34 Tyr)bPTH-(3-34)amide, in the PTH-responsive osteoblastic cell line UMR-106. Northern blot analysis of tumor extracts revealed the presence of PTHrP mRNA transcripts, while PTH mRNA was undetectable. In contrast, neither PTHrP mRNA(s) nor cAMP-stimulating activity was detectable in other neuroendocrine tumors not accompanied by hypercalcemia. These results demonstrate that certain pancreatic neuroendocrine tumors associated with hypercalcemia can synthesize and release PTHrP.
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PMID:Parathyroid hormone-related protein and hypercalcemia in pancreatic neuro-endocrine tumors. 239 7

We have demonstrated that T3M-1 cells and T3M-5 cells, derived from squamous carcinomas of patients with leukocytosis and hypercalcemia, produced excessively G-CSF, IL-1 alpha and a small amount of PTH-like factor. We confirmed that G-CSF and IL-1 alpha (hemopoietin 1) enhanced granulocytopoiesis and caused marked leukocytosis in vivo. Furthermore, we also demonstrated that PTH-rP and IL-1 alpha (a potent osteoclast-activating factor) synergistically stimulated bone resorption in vitro and also synergistically increased serum calcium concentration in vivo. Since we have demonstrated that at least two clonal cell lines derived from patients with hypercalcemia and leukocytosis produced G-CSF and IL-1 alpha, we presume that hypercalcemia and leukocytosis associated with some solid tumors may constitute a new paraneoplastic syndrome.
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PMID:A paraneoplastic syndrome of hypercalcemia and leukocytosis associated with solid tumors: production of interleukin 1 alpha (IL-1 alpha) and granulocyte colony-stimulating factor (G-CSF) by clonal squamous cell carcinoma cells. 247 Jun 24

Previously we reported that a clonal squamous cell carcinoma cell line (T3M-1) derived from a lower jaw cancer of a patient with marked leukocytosis and hypercalcemia produced factors containing a potent bone-resorbing activity (BRA) (Mr 15,000-20,000) and a colony-stimulating activity. To elucidate the pathogenesis of this humoral hypercalcemia, BRA and colony-stimulating activity in both the conditioned medium and cells were characterized. The conditioned medium, when eluted at neutral pH, contained colony-stimulating activity and thymocyte proliferation-stimulating activity, the latter of which comigrated with BRA. Upon elution with acetic acid (pH 2.0), the conditioned medium contained no interleukin 1-like activity but potent parathyroid hormone-like activity, which comigrated with BRA. Northern blot hydridization analysis revealed that T3M-1 cells produced constitutively mRNA for parathyroid hormone-related protein and granulocyte colony-stimulating factor. Furthermore, primer extension analysis revealed that the cells also produced mRNA for interleukin 1 alpha (IL-1 alpha). Since parathyroid hormone-related protein and IL-1 alpha (osteoclast-activating factor) synergistically increase the concentration of serum calcium, and since IL-1 alpha (hemopoietin 1) potentiates granulocyte colony-stimulating factor-induced granulocytopoiesis, we speculate that parathyroid hormone-related protein, granulocyte colony-stimulating factor, and IL-1 alpha are synergistically involved in a paraneoplastic syndrome of hypercalcemia and leukocytosis, at least in some patients with solid tumors.
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PMID:Paraneoplastic syndrome of hypercalcemia and leukocytosis caused by squamous carcinoma cells (T3M-1) producing parathyroid hormone-related protein, interleukin 1 alpha, and granulocyte colony-stimulating factor. 247 71

The effects of three synthetic amino-terminal fragments of human parathyroid hormone-related peptide (hPTHrP) on cytosolic free calcium ([Ca2+]i) mobilization and intracellular cAMP production were investigated and compared with those of human PTH(1-34) in opossum kidney (OK) cells. The mean basal [Ca2+]i in OK cells was 115 +/- 7.8 nM (mean +/- SE, n = 30). Human PTHrP(1-34), [40Tyr]hPTHrP(1-40) and hPTH(1-34) significantly (P less than 0.01) raised [Ca2+]i to 149 +/- 3, 150 +/- 5 and 148 +/- 6% of the basal value, respectively (mean +/- SE, n = 3). These three peptides showed similar dose dependency at concentrations between 10(-10) and 10(-7) M. These increases appeared to be, in part, due to mobilization from intracellular calcium stores. On the other hand, these three peptides also stimulated intracellular cAMP production in an equipotent manner in OK cells. However, both 10(-3) M dibutyryl cAMP and 10(-5) M forskolin failed to cause an increase in [Ca2+]i. Furthermore, [40Tyr]hPTHrP(3-40) neither affected the intracellular cAMP content significantly nor caused an increase in [Ca2+]i. These results indicate that hPTHrP mimics PTH by activating a dual second messenger system ([Ca2+]i and cAMP) in OK cells, and that [Ca2+]i stimulation by hPTHrP and hPTH is independent of cAMP production. Additionally, N-terminal amino acid position 1 to 2 of hPTHrP appears to play a crucial role in both [Ca2+]i stimulation and cAMP production.
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PMID:The effects of human parathyroid hormone-related peptide on cytosolic free calcium and cAMP production in opossum kidney cell. 248 98

PTH-related protein (PTHrP), similarly to PTH, stimulates cAMP production in target tissues. However, different potencies have been observed for the two peptides in some biological assays, suggesting that cAMP-independent second messenger pathways might be involved in PTHrP signal transduction. This hypothesis was tested in the osteogenic sarcoma cell line UMR 106-01. Addition of PTHrP-(1-34) to cell suspensions loaded with the Ca2+ indicator indo-1 produced a transient dose-dependent increase in intracellular calcium ([Ca2+]i), with a maximal effect at 2 x 10(-7) M and an ED0.5 at about 4 x 10(-8) M. The amplitude and duration of the transients were similar to those induced by equimolar concentrations of bovine PTH-(1-34) (bPTH), and the dose-responses of the two peptides completely overlapped. Both full-length peptides, PTHrP-(1-141) and bPTH-(1-84), produced effects identical to those observed with the 1-34 fragments. Homologous and heterologous desensitization to both PTHrP-(1-34) and PTHrP-(1-141) occurred when the cells were prestimulated with equimolar or 10-fold lower doses of either PTHrP-(1-34) or bPTH-(1-34). Desensitization to bPTH-(1-34) was also observed when cells were prestimulated with PTHrP-(1-34). Furthermore, pretreatment with either bPTH-(3-34) or [Nle8,18, Tyr34]bPTH-(3-34) amide did not affect [Ca2+]i, but reduced the response to PTHrP-(1-34) by 55 +/- 10% (n = 3) and 67 +/- 8% (n = 3), respectively. The PTHrP-(1-34)-induced [Ca2+]i transient was not substantially affected by either extracellular Ca2+ chelation by EGTA or pretreatment with diltiazem, and nitrendipine only partially inhibited the [Ca2+]i response to PTHrP-(1-34) by about 10%. These results indicate that in osteoblastic cells PTHrP mobilizes Ca2+ from an intracellular storage pool with potency equal to that of PTH, and that the two hormones interact with the same receptor.
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PMID:Parathyroid hormone-related peptide transiently increases cytosolic calcium in osteoblast-like cells: comparison with parathyroid hormone. 250 65

PTH-like proteins (PTHLP), which are associated with humoral hypercalcemia of malignancy, have recently been purified. Isolation of their corresponding cDNAs has revealed that they are derived from a single gene. In this report a synthetic gene encoding PTHLP-(1-141), a 141-amino acid protein corresponding to the most abundant PTHLP cDNA detected in human tumors, was expressed in bacteria and purified to homogeneity. Recombinant (r) PTHLP-(1-141) migrates with an aberrantly high mol wt on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, presumably as a result of its unusually basic pI. rPTHLP-(1-141), like PTH, induced hypercalcemia in rats, caused release of 45Ca from fetal rat bones, and stimulated the synthesis of cAMP by rat osteosarcoma cells and canine renal membrane preparations. A comparison of the abilities of rPTHLP-(1-141) and bovine PTH-(1-34) to stimulate cAMP synthesis indicated rPTHLP-(1-141) to be 5-fold more potent in the osteosarcoma assay, while nearly 30-fold less active in the renal membrane adenylate cyclase assay. Although 100-fold less potent than bovine PTH-(1-34) in promoting bone resorption, rPTHLP-(1-141) was a potent calcemic factor in vivo, inducing a rise in serum calcium from 10.4 to 14.5 mg/dl when infused into rats at 1.3 micrograms/h. These results support previous assumptions that PTHLP is the humoral factor responsible for humoral hypercalcemia of malignancy. In addition, they suggest substantial differences between PTHLP and PTH in the regulation of calcium homeostasis.
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PMID:Synthesis of a gene encoding parathyroid hormone-like protein-(1-141): purification and biological characterization of the expressed protein. 253 1


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