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PubMed1987

[Reproduction and differentiation of cells in the tissues of growing rat teeth in response to parathyroid hormone and hydrocortisone].

Influence of parathyroid hormone (PTH) and hydrocortisone (HC) on growth and development of teeth during prefunctional period has been studied, employing radioactive tracers. Biosynthetic and reproductive activity of cells is estimated in the molar and incisor tissues. It has been established that PTH accelerates the process of local resorption of the bone along the alveolar crest, but does not influence upon the teeth growth, functional and reproductive activity of the pulp cells. HC inhibits protein and glycoprotein synthesis, decreases amount of proliferating cells, accelerates their differentiation and, thus, delays formation of the root and tooth growth.

Ameloblasts↗
PubMed1977

[A symptomatic parathyroid adenoma. Value of parathyroid hormone determination through selective catheterization of the thyroid veins].

A parathyroid adenoma is reported in a girl aged 12 years in whom hypercalcaemia was discovered by chance. Investigation of calcium metabolism suggested the diagnosis of hyperparathyroidism and studies of the urinary cyclic AMP and determination of the plasma parathyroid hormone concentration further added to the evidence. The diagnosis of parathyroid adenoma was made after determination of the parathyroid hormone concentration at various sights during selective catheterization of the tyroid veins. This was confirmed at surgery. In this patient the place of catheterization of the inferior thyroid veins in the early diagnosis of primary hyperparathyroidism is discussed.

Adenoma↗
PubMed1975

Relationship between the kidney and parathyroid hormone.

This report reviews the interrelationship between the activity of the parathyroid glands and renal function. Among the topics discussed are: effects of parathyroid hormone on various aspects of renal function such as: (1) glomerular filtration rate and renal blood flow; (2) renal handling of phosphorus, calcium, magnesium, sodium and potassium; (3) renal production of 1,25-dihydroxycholecalciferol; (4) renal handling of bicarbonate and acid-base metabolism, and (5) mechanism of action of parathyroid hormone on the renal cell. Further topics include: renal metabolism of parathyroid hormone; the kidney in hyperparathyroidism, and effects of renal failure on structure and function of the parathyroid glands.

Acid-Base Equilibrium↗
PubMed2007

Development of a rat parathyroid hormone 2 receptor antagonist.

The parathyroid hormone 2 (PTH2) receptor is a Family B G-protein coupled receptor most highly expressed within the brain. Current evidence suggests that tuberoinfundibular peptide of 39 residues (TIP39) is the PTH2 receptor's endogenous ligand. To facilitate investigation of the physiological function of the PTH2 receptor/TIP39 system, we have developed a novel PTH2 receptor antagonist, by changing several residues within the amino terminal domain of TIP39. Histidine(4), tyrosine(5), tryptophan(6), histidine(7)-TIP39 binds the PTH2 receptor with high affinity, has over 30-fold selectivity for the rat PTH2 receptor over the rat PTH1 receptor and displays no detectable agonist activity. This ligand should be useful for in vivo investigation of PTH2 receptor function.

Amino Acid Sequence↗
PubMed1987

Radioimmunoassay for parathyroid hormone in equids.

Radioimmunoassay for parathyroid hormone (PTH) in equids was performed on blood samples from healthy equids and equids with hypercalcemia and hypophosphatemia. The assay was validated for equine carboxy-terminal PTH. Manipulation of serum ionized Ca in healthy equids by infusing Na2 EDTA and CaCl2 produced an expected increase and decrease, respectively, in measurable immunoreactive PTH. Intra-assay and interassay coefficients of variation were 2.6% and 11.7%, respectively. The range of PTH valves for healthy mature horse mares and geldings maintained on pasture was less than 0.27 ng/ml to 0.92 ng/ml and for horse colts fed grain was 0.61 to 1.25 ng/ml. Serum PTH values were measured on 2 equine patients with hypercalcemia, 1 pony with primary hyperparathyroidism and 1 horse with pseudohyperparathyroidism. Both patients had increased serum PTH values.

Animals↗
PubMed2003

[High expression and characterization of human parathyroid hormone in Escherichia coli].

Human parathyroid hormone (hPTH) was highly expressed in Escherichia coli by inserted the synthesized whole hPTH cDNA into the vectors pBV220 and pET22b. After expression and disruption, the purified product was acquired through cation exchange chromatography and reverse phase chromatography. From the results of N-terminal sequencing and MALDI-TOF-MS analysis the recombiant prtein was indentified as intact hPTH. In in vitro Bioassays the recombinant hPTH stimulated adenylate cyclase as the standard did. In ovariectomized rats the recombinant hPTH markedly increased the femoral bone mass and bone mineral density.

Amino Acid Sequence↗
PubMed1990

Expression of human parathyroid hormone in Escherichia coli.

Human parathyroid hormone (hPTH) is a peptide hormone consisting of 84 amino acids. Using the expression plasmid pKK223-3 with the strong tacpromoter, we have produced a variant of hPTH in E. coli. From the expression plasmid construct the expected product was hPTH with an N-terminal extension of Met-Gly. The peptide was extracted from E. coli cells and purified by high performance liquid chromatography. In two different gel electrophoresis systems including identification by immunoblotting the product behaved exactly as an hPTH standard. N-terminal amino acid sequence analysis of the purified product showed traces of Gly-hPTH. At least 90% of the expressed product was N-terminally blocked, suggesting the presence of N-formyl-methionine. This variant of hPTH did not stimulate adenylate cyclase activity in rat osteosarcoma cell membranes.

Adenylyl Cyclases↗
PubMed2005

Role of matrix Gla protein in parathyroid hormone inhibition of osteoblast mineralization.

Parathyroid hormone (PTH) exerts biphasic effects on bone, dependent on the frequency and dose of administration. The catabolic actions of PTH on bone have been associated with continuous treatment, an increase in osteoblast-mediated resorption of bone via osteoclast activation, and inhibition of osteoblast activity and mineralization. Downregulation of differentiation markers and inhibition of mineralization by PTH have been reported in primary calvarial explants and osteoblast cell lines. Using MC3T3-E1 osteoblast-like cells, we have shown that matrix Gla protein (MGP) can be induced by PTH, and that this induction may explain the PTH-mediated inhibition of osteoblast biomineralization. MGP is a known inhibitor of mineralization, and mice deficient in Mgp show severe vascular calcification and premature bone mineralization. This review discusses the role of MGP in mineralization, comparing bone and vascular mineralization. In addition to MGP, the regulation and possible role of osteopontin, another known regulator of osteoblast mineralization, in PTH-mediated regulation of bone and vascular mineralization is discussed.

Animals↗
PubMed1975

Radioimmunoassay of bovine parathyroid hormone.

A radioimmunoassay of bovine parathyroid hormone (PTH) was developed, using guinea pig antiserum against bovine PTH and highly purified 125I-labeled bovine PTH. The 125I-labeled PTH which had been purified by antiserum against PTH had higher sensitivity than that purified by the adsorption method with microfine precipitated silica Quso G 32. An equilibrium and an unequilibrium incubation methods were used comparatively. 125I-labeled PTH was incubated at the same time, with antiserum against PTH, and a sample in the former and added after preincubation in the latter, which gave better results than the former. By the unequilibrium incubation method, the plasma PTH level was measured in nonpregnant cows infused experimentally with ethylenediamine tetraacetic acid (EDTA) and untreated pregnant cows 2 to 30 days before parturition. As a result, plasma PTH levels were raised after EDTA infusion. The plasma PTH levels in cows of the late stage of pregnancy were 1.16 +/- 0.93 ng/ml. A reciprocal relationship was observed between plasma PTH and calcium levels. It was statistically significant with an inverse correlation coefficient of -0.661 (P less than 0.001).

Animals↗
PubMed2001

Implant fixation enhanced by intermittent treatment with parathyroid hormone.

The intermittent administration of parathyroid hormone (PTH) increases the formation of bone by stimulating osteoblastic activity. Our study evaluates the possibility that intermittent treatment with PTH (1-34) may also enhance the implant-bone fixation of stainless-steel screws. Twenty-eight rats received one screw in either one (n = 8) or in both (n = 20) proximal tibiae. We administered either PTH (1-34) in a dosage of 60 microg/kg/day (n = 14) or vehicle (n = 14) over a period of four weeks. At the end of this time, the degree of fixation was assessed by measuring the removal torque on one screw in each rat (n = 28) and the pull-out strength on the contralateral screw (n = 20). PTH increased the mean removal torque from 1.1 to 3.5 Ncm (p = 0.001) and the mean pull-out strength from 66 to 145 N (p = 0.002). No significant differences in body-weight or ash weight of the femora were seen. Histological examination showed that both groups had areas of soft tissue at the implant-bone interface, but these appeared less in the PTH group. These results indicate that intermittent treatment with PTH may enhance the early fixation of orthopaedic implants.

Animals↗
PubMed1985

Inhibition of human platelet aggregation by parathyroid hormone. Is cyclic AMP implicated?

Parathyroid hormone (PTH) is a polypeptide which in different in vitro systems raises intracellular cyclic AMP (cAMP) levels via adenyl cyclase activation and stimulates Ca2+ transport across cell membranes. We tested whether, on the basis of this mechanism, PTH would inhibit human platelet aggregation. The latter was tested in vitro by a photometric technique. Platelet aggregation induced by the calcium ionophore A 23187 was inhibited by PTH at concentrations (0.5-3 USP U/ml) similar to those effective in other in vitro systems. Higher concentrations of PTH were required to prevent aggregation initiated by adenosine-5'-diphosphate, arachidonic acid, or platelet-aggregating factor. The terminal synthetic fragment 1-34 b PTH was ineffective against all aggregation stimuli. The antiaggregating effect of PTH was potentiated by verapamil and theophylline and was additive to that of PGI2. However, PTH did not appear to increase platelet cAMP levels and was not counteracted by an inhibitor of platelet adenyl cyclase. It is therefore unlikely that PTH inhibits platelet aggregation through an adenyl cyclase stimulated increase of cAMP. Since PTH levels are markedly increased in uremic plasma, it might contribute to the defective platelet function and the bleeding tendency frequently occurring in uremic patients.

Adenylyl Cyclases↗
PubMed1990

Mechanisms of the vascular action of parathyroid hormone.

The vasodilatory effect of parathyroid hormone (PTH) has been investigated repeatedly and confirmed over the past few years. The present study correlates the PTH-induced vasodilatory effect with the biochemical changes in cyclic AMP (cAMP) content and Ca++ uptake in the vascular tissue. Synthetic fragment bPTH-(1-34) (1.2 X 10(-7) M) significantly inhibited the contraction of the isolated tail artery of rat induced by KCl (30-80 mM). It also relaxed KCl (40 and 60 mM)-induced contractions in a concentration-dependent manner [2.7 X 10(-9) to 3.7 X 10(-8) M)]. In addition, the concentration-contraction curve of Ca (0.3-3.0 mM) was shifted to the right by PTH in 40 mM KCl Krebs-Henseleit solution. These suggest the blocking effects of PTH on Ca entry. This hypothesis was supported by a study in which PTH inhibited KCl-enhanced 45Ca uptake, an effect similar to that of D600. In the experiment with matched tissue, PTH increased tissue cAMP content whereas KCl did not. These suggest that the vascular actions of PTH may involve both cAMP and Ca entry blocking. It is important to know that PTH was capable of stimulating cAMP content in Ca-free medium, suggesting that the increase in cAMP level by PTH may not be secondary to the change in Ca++ uptake.

Animals↗
PubMed1996

Effects of parathyroid hormone on renal tubular proteinases.

Parathyroid hormone (PTH) has been implicated to exert detrimental effects on remnant nephrons in chronic renal failure. The present investigation addressed the influence of PTH on the proteolytic capacity of isolated proximal tubules both from normal (SHAM) and partially nephrectomized rats (5/6-NX). Proteolytic activities were measured either against azocasein (pH 5.4) or with specific fluorogenic peptidyl substrates for individual cysteine proteinases. Azocaseinolytic activity was enhanced 6 weeks after 5/6-NX in tubules (SHAM 19.0 +/- 1.0 vs. 5/6-NX 24.4 +/- 1.5 U/mg protein), while thereafter activities declined progressively with time (5/6-NX 16 weeks: 12.9 +/- 1.2 U/mg protein). This loss in proteolytic activity could almost completely be prevented by parathyroidectomy (PTX) (5/6-NX + PTX 16 weeks: 18.6 +/- 1.1 U/mg protein). By contrast, severe hyperparathyroidism (induced by a low calcium/high phosphorus diet fed for 6 weeks) in 5/6-NX animals resulted in a significant decline in proteolytic activities in remnant tubules (5/6-NX 24.4 +/- 1.5 vs. 5/6-NX+diet 16.4 +/- 1.9 U/mg protein). When specific activities of tubular cathepsins were measured in healthy rats who had received exogenous PTH, each individual cysteine proteinase (cathepsin L: -42%; cathepsin B: -27%; cathepsin H: -51%) was suppressed. This effect of PTH could readily be abolished by the simultaneous administration of verapamil. These results suggest that chronic PTH excess exerts a suppressive effect on tubular proteinase activities both in normal and partially nephrectomized rats. This PTH effect seems to be mediated by an increase of cytosolic calcium.

Animals↗
PubMed1996

Domain-specific gene activation by parathyroid hormone in osteoblastic ROS17/2.8 cells.

Parathyroid hormone (PTH)-mediated gene activation was assessed in the osteoblast-like rat cell line ROS17/2.8 with two PTH fragments harboring distinct activating domains: PTH-(1-34) and PTH-(28-48). The PTH response of genes expressed immediate early in the cell cycle or in the osteoblast developmental sequence was investigated. In addition, subtractive cloning was used to identify genes in ROS17/2.8 cells that are activated by the two PTH domains. PTH-(1-34) immediately increased the transcript levels of c-fos and c-jun at a considerably higher rate than PTH-(28-48). A significant immediate PTH effect on osteoblastic marker genes could not be detected, with the exception of elevated ornithine decarboxylase transcript levels. However, continuous application of PTH-(1-34) increased transcript levels of the osteoblast-specific osteocalcin gene and reduced those of other osteoblastic marker genes including alkaline phosphatase and the PTH/PTH-related peptide receptor. By subtractive cloning, nine cDNAs were isolated corresponding to mRNAs directly up-regulated by PTH-(1-34) or PTH-(28-48). Among these were a cyclic phosphodiesterase, a (cytosine 5)-methyltransferase, an 80-kDa protein kinase C substrate, junB, and a novel GC-binding protein. Three cDNAs are unknown at present. Interestingly, in all cases, the efficiency of gene activation by PTH-(28-48) was substantially lower in comparison with PTH-(1-34). PTH-mediated protein kinase C signaling in ROS17/2.8 cells may therefore constitute a minor pathway in comparison with the dominant cAMP/protein kinase A cascade.

Animals↗
PubMed1997

E64d, a membrane-permeable cysteine protease inhibitor, attenuates the effects of parathyroid hormone on osteoblasts in vitro.

Parathyroid hormone (PTH) activates calpains I and II (calcium-activated papain-like proteases) and stimulates the synthesis and secretion of cathepsin B (a lysosomal cysteine protease) in osteoblastic cells. Anabolic doses of PTH also stimulate osteoprogenitor cell proliferation and differentiation into mature, fully functional osteoblasts capable of elaborating bone matrix, whereas catabolic doses of PTH stimulate calcium mobilization and matrix turnover. Previous investigations in other cell types have demonstrated that calcium-activated calpains play a major role in regulating proliferation and differentiation by catalyzing limited regulatory proteolysis of nuclear proteins, transcription factors, and enzymes. We tested the hypothesis that inhibition of intracellular cysteine proteases such as the calpains will ablate PTH-mediated osteoblast proliferation and differentiation, two fundamental indices of bone anabolism. A brief preincubation with the membrane-permeable, irreversible cysteine protease inhibitor E64d (10 micrograms/mL) before short-term PTH treatment blunted PTH-induced cell proliferation in subconfluent cultures and also attenuated proliferation and inhibited differentiation in longer-term confluent cultures. This confirms the hypothesis that cysteine proteases such as the calpains are important in mediating the proliferative and prodifferentiating or anabolic effects of PTH on MC3T3-E1 cells in culture. Immunofluorescent localization demonstrated that calpain I, calpain II, and calpastatin (the endogenous calpain inhibitor) are abundant and widely distributed within actively proliferating MC3T3-E1 preosteoblasts. Since the calpains are active and stable at neutral intracellular pH levels in osteoblasts, whereas cathepsins are not, our results support a role for these calcium-activated regulatory proteases in mediating the anabolic effects of PTH in bone.

Alkaline Phosphatase↗
PubMed1991

Measurement of intracellular Ca2+ in single aequorin-injected and suspensions of fura-2-loaded ROS 17/2.8 cells and normal human osteoblasts. Effect of parathyroid hormone.

It is known that parathyroid hormone (PTH) activates the cyclic AMP (cAMP) signalling pathway in osteoblasts. In recent years it has been suggested that an elevation of the intracellular free Ca2+ concentration ([Ca2+]i) may also be involved in the regulation of osteoblast function by PTH. However, this remains controversial. Here we investigated the effect of PTH on the [Ca2+]i of ROS 17/2.8 cells and normal human osteoblasts. The [Ca2+]i was measured in single aequorin-injected cells and in suspensions of cells loaded with fura-2. Human PTH-(1-38)-peptide (1-300 nM) had no effect on the [Ca2+]i in single aequorin-injected ROS 17/2.8 cells (n = 17) measured at various times after injection (1-20 h), or in suspensions of fura-2-loaded ROS 17/2.8 cells (n = 9). Ionomycin (1 microM) increased the [Ca2+]i in fura-2-loaded and single aequorin-injected ROS 17/2.8 cells by 285 +/- 60 nM (n = 9) and 312 +/- 99 nM (n = 6) respectively, indicating that both methods detect changes in [Ca2+]i with equal sensitivity. In contrast, human PTH-(1-38) (10-100 nM) markedly stimulated cAMP accumulation in ROS 17/2.8 cells. In single aequorin-injected normal human osteoblasts there was no change in the [Ca2+]i in response to 100 nM human PTH-(1-38) or 100 nM bovine PTH-(1-84) (n = 18). In contrast, in suspensions of normal human osteoblasts loaded with fura-2, an increase in [Ca2+]i in response to human PTH-(1-38) (100 nM) was found (60 +/- 28 nM; n = 6). Considerable variation in the magnitude of the response was observed between individual preparations and donors. These data indicate that PTH activates cAMP accumulation without affecting [Ca2+]i in ROS 17/2.8 cells and that PTH causes a rise in [Ca2+]i only in a small subset of normal human osteoblasts. We suggest that the Ca2+ response to PTH in osteoblasts is limited by the state of differentiation of the cells, and may be due either to the presence of a distinct Ca2(+)-mobilizing receptor or to a cAMP-mediated Ca2+ response.

Aequorin↗
PubMed1978

Parathyroid hormone and calcitonin in serum of patients with mammary carcinoma.

Immunoreactive parathyroid hormone and calcitonin in serum were measured in 34 normocalcemic patients with mammary carcinoma. The mean value of parathyroid hormone was significantly higher in 26 patients with bone metastases than in 8 patients without (p less than 0.025). One patient with bone metastases had slightly raised calcitonin in serum. No difference as to parathyroid hormone values between the groups of previously irradiated and non-irradiated patients was found. A possible explanation of the normocalcemic hyperparathyroidism is presented.

Adult↗
PubMed1972

Parathyroid Hormone in Human Plasma: IMMUNOCHEMICAL CHARACTERIZATION AND BIOLOGICAL IMPLICATIONS.

Antigenic recognition of four anti-bovine parathyroid hormone antisera was characterized by their reactivity with bovine hormonal fragments (1-34, 1-13, 14-34, 19-34, 53-84) and human hormone extracted from parathyroid adenomas. All antisera were found to have antibody populations which recognized more than one antigenic determinant and all antisera differed in their specificity and reactivity for the fragments of bovine hormone. By modification of two antisera, GP-1 and GP-133, by preincubation with excess concentrations of 1-34 or 53-84 fragments, antigenic recognition was restricted to defined regions of the hormonal sequence.When assays using these modified antisera were applied to the study of hormones extracted from glands, greater immunochemical similarities were seen between bovine and human parathyroid hormone using assays that were specific for the measurement of amino-terminal portions of the hormones than of the carboxy-terminal portions.When assays using these antisera were applied to the study of endogenous parathyroid hormone in human plasma, the immunoreactive hormone in the general circulation was shown to substantially lack an amino-terminal portion of the sequence of the intact hormone, including an antigenic determinant requiring all or some of the 14-19 region. This deletion accounts, at least in part, for the immunochemical heterogeneity of plasma parathyroid hormone in man. Radioimmunoassay of fractions of peripheral plasma subjected to gel filtration confirms that the dominant form of the immunoreactive hormone in the general circulation of man is a hormonal fragment that is totally devoid of amino-terminal reactivity. Because of this deletion, it can be concluded that most of the immunoreactive parathyroid hormone in the general circulation of man must be biologically inactive.

Journal Article↗