Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

PTH release from bovine parathyroid cells is inhibited by increasing concentrations of extracellular calcium (Ca2+). We have proposed that this inhibition is mediated by Ca2+ channels via a G-protein. To further test this hypothesis, we evaluated the effect of lanthanum (La3+), a potent Ca2+ channel antagonist that does not cross the cell membrane. PTH release was determined in dispersed bovine parathyroid cells by radioimmunoassay: extracellular Ca2+ concentration was 0.2 mM. PTH release was inhibited by maximal concentrations of La3+ to a greater extent than by Ca2+: 93% inhibition by La3+ vs. 40% by Ca2+. La3+ was more potent (set-point = 0.12 mM) than Ca2+ (set-point = 1.2 mM). Incubation of parathyroid cells with pertussis toxin, which inactivates a G-protein(s) and blocks inhibition by Ca2+, did not block the inhibition of PTH release by La3+ at the concentrations tested. The Ca2+ ionophore A23187, which potentiates the effect of Ca2+, did not enhance the inhibition of PTH release by La3+. Increasing concentrations of calcium enhanced the inhibition of PTH release by the Ca2+ channel agonist, (+)202-791. The Ca2+ channel antagonist, (-)202-791, shifted the Ca2+ inhibition curve to the right. La3+ did not alter the inhibition of PTH release by the Ca2+ channel agonist but blocked the stimulatory effect of the Ca2+ channel antagonist, (-)202-791. In summary: 1) La3+, which blocks Ca2+ channels and does not cross cell membranes, effects a greater inhibition of PTH release than Ca2+; 2) La3+, like Ca2+, overrides the effect of Ca2+ channel antagonist (-)202-791; and 3) La3+, unlike Ca2+, inhibits PTH release by a mechanism that is independent of a pertussis toxin-sensitive G-protein. There may be two cell surface sites that recognize La3+ and Ca2+ independently.
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PMID:Differences in the actions of calcium versus lanthanum to influence parathyroid hormone release. 211 32

PTHrP(7-34)NH2 and [D-Trp12]PTHrP(7-34)NH2 have previously been shown to be shown to be more potent antagonists than the corresponding PTH peptide, [Tyr34]bPTH(7-34)NH2. However, these peptides also display partial agonism for adenylate cyclase activity in ROS 17/2.8 cells. In this study, design of a pure potent antagonist of PTH and PTHrP by removal of agonism from PTHrP(7-34)NH2 with retention of antagonist potency was accomplished. Since [Tyr34]bPTH(7-34)NH2 lacks agonist activity, we introduced two amino acids native to the PTH sequence into their respective positions in PTHrP and the potent D-Trp12 analog. [Asn10Leu11]- and [Asn10,leu11,D-Trp12]-PTHrP(7-34)NH2 were found to be 23- and 26-fold more potent as antagonists in ROS cells than PTHrP(7-34)NH2 and [D-Trp12]PTHrP(7-34)NH2, respectively. In addition, these peptides did not display partial agonism, even in an assay based on highly responsive cells pretreated with dexamethasone and pertussis toxin. In contrast, when the PTHrP sequence Asp10,Lys11 was inserted into [Tyr34]hPTH(7-34)NH2, antagonist potency declined by more than 6-fold and PTH-like agonist activity was installed. These results demonstrate that the activation domain of both PTH and PTHrP can be extended to include the 1-12 region and that the 10-12 region, in addition to the N-terminal hexapeptide, is important not only for receptor binding but also for hormonal signal transduction.
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PMID:Removal of partial agonism from parathyroid hormone (PTH)-related protein-(7-34)NH2 by substitution of PTH amino acids at positions 10 and 11. 216 25

In the design and biological evaluation of PTH antagonists, certain analogs, although antagonists in vitro, possess partial agonist properties in vivo that preclude their utility as antagonists. In an effort to identify weak agonism of PTH analogs, an attempt was made to enhance the responsiveness of the widely employed rat osteosarcoma (ROS 17/2.8) cell adenylate cyclase assay. Because responsiveness to PTH in these cells is enhanced upon treatment with dexamethasone (dex) or pertussis toxin (PT), we have evaluated their use to aid in detection of partial agonism for PTH and PTH-related protein (PTHrP) antagonist analogs. Treatment of cells with dex alone (30 nM for 3 days) or with PT alone (40 ng/ml for 1 day) increased basal adenylate cyclase activity by 27%. However, combination of the dex and PT treatments increased basal cAMP production 70%. The in vivo partial agonist [Nle8,18,Tyr34]bPTH(3-34)NH2 increased cAMP production 3-fold over basal levels in untreated cells, nearly 5-fold in PT-treated cells, 8-fold in cells treated with dex, and 10-fold in cells treated with dex plus PT. Similar results were obtained with PTHrP(7-34)NH2: the 6-fold stimulation observed in control cells was converted to 14-fold in cells treated with dex plus PT. Agonist activity undetectable in the conventional assay was observed in the dex plus PT system: [Tyr34]- and [D-Trp12,Tyr34]bPTH(7-34)NH2, which exhibit no agonist activity under control conditions, stimulated cAMP production 2.6- and 2.1-fold, respectively, under dex plus PT treatment. In contrast, the antagonist analogs [Asn10,Leu11]- and [Leu11,D-Trp12]PTHrP(7-34)NH2, hybrid peptides of PTH and PTHrP, had no agonist activity under any conditions. Because of increased responsiveness, this assay should occupy an important step in the pathway for evaluation of PTH antagonists and permit identification of weak partial agonist activity before extensive in vivo testing.
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PMID:Treatment of bone-derived ROS 17/2.8 cells with dexamethasone and pertussis toxin enables detection of partial agonist activity for parathyroid hormone antagonists. 216 26

We compared the effects of a series of di- and trivalent cations on various aspects of parathyroid function to investigate whether these polyvalent cations act on the parathyroid cell through a similar mechanism. Like high extracellular concentrations of Ca2+, high levels of barium (Ba2+), strontium (Sr2+), gadolinium (Gd3+), europium (Eu3+), terbium (Tb3+), and ytterbium (Yb3+) [corrected] each inhibited low calcium-stimulated PTH release and showed IC50 values (the concentration producing half of the maximal inhibitory effect) of 1.12 mM, 1.18 mM, 2.2 microM, 2.5 microM, 0.89 microM, and 15 microM, respectively. The inhibitory effects of both divalent (Ca2+ and Ba2+) and trivalent (Gd3+) cations were reversible by 76-100% after removal of the cation, suggesting that the polyvalent cation-mediated reduction in PTH release was not due to nonspecific toxicity. The same di- and trivalent cations produced an 80-90% decrease in agonist-stimulated cAMP accumulation with a similar order of potency as for their effects on PTH release. Preincubation overnight with pertussis toxin totally prevented the inhibitory effects of the trivalent cations on cAMP accumulation. The same di- and trivalent cations also increased the accumulation of inositol monophosphate, inositol bisphosphate, and inositol trisphosphate. Their effects on this parameter differed from those on PTH release and cAMP accumulation in several respects. First, Ba2+ and Sr2+, rather than being equipotent with Ca2+, were about 2-fold less potent in increasing the levels of inositol phosphates. Second, the trivalent cations were 5-50-fold less potent in raising inositol phosphates than in modulating PTH release and cAMP accumulation, and all were nearly equipotent. These results show that trivalent cations of the lanthanide series mimic the actions of divalent cations on several aspects of parathyroid function, and likely do so by interacting with the cell surface "Ca2(+)-receptor-like mechanism" through which extracellular Ca2+ has been postulated to act. The pharmacology of the effects of these polyvalent cations on cAMP and PTH release are similar and differ from that for their actions on inositol phosphate metabolism, raising the possibility that there might be more than one form of the putative Ca2+ receptor.
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PMID:A comparison of the effects of divalent and trivalent cations on parathyroid hormone release, 3',5'-cyclic-adenosine monophosphate accumulation, and the levels of inositol phosphates in bovine parathyroid cells. 216 4

In the present studies, we used fluoride and pertussis toxin, potent modulators of guanine nucleotide binding proteins (G proteins), to examine the role of G proteins, cytosolic calcium ([Ca]i) and cAMP in the regulation of PTH secretion from dispersed bovine parathyroid cells. NaF suppressed PTH secretion and cAMP content and increased [Ca]i levels in a dose-dependent manner. Prior removal of extracellular calcium with EGTA completely blocked the NaF-induced increase in [Ca]i, but did not prevent the NaF-induced inhibition of PTH secretion and cAMP content. Pretreatment with 10(-5) M verapamil or 10(-4) M diltiazem blocked neither the NaF-induced suppression of PTH secretion and cAMP content nor the increase in [Ca]i. Manganese chloride (10(-4) M) significantly inhibited the NaF-induced increase in [Ca]i, but did not block the NaF-induced suppression of PTH secretion and cAMP content. Pertussis toxin blocked neither the NaF-induced increase in [Ca]i nor suppression of PTH secretion and cAMP content. Our data suggest that (1) NaF might stimulate a calcium channel resulting in the increase in [Ca]i by acting on a G protein in a manner resistant to the inhibition by pertussis toxin; (2) the NaF-induced increase in [Ca]i is not directly linked to the suppression of PTH secretion, and (3) the NaF-induced suppression of PTH secretion might be explained at least in part by the decrease in cell cAMP content.
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PMID:Role of guanine nucleotide binding protein, cytosolic calcium and cAMP in fluoride-induced suppression of PTH secretion. 217 17

Parathyroid hormone secretion is negatively regulated by calcium. We utilized calcium channel agents: +202-791, a calcium channel agonist and -202-791, a calcium channel antagonist, to evaluate the role of calcium channels in PTH secretion. +202-791 inhibited PTH release from bovine parathyroid cells and the antagonist stimulated release. Incubation with pertussis toxin which ADP-ribosylates and inactivates a guanine nucleotide regulatory protein (G-protein) releases the inhibition by the calcium channel agonist. These findings indicate that a G-protein is interposed between the calcium channel and a putative intracellular site controlling PTH secretion.
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PMID:Control of PTH secretion is mediated through calcium channels and is blocked by pertussis toxin treatment of parathyroid cells. 242 80

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] regulates the synthesis of bone gamma-carboxyglutamic acid (Gla) protein (BGP) by osteoblastic cells. In this study we examined the effect of cAMP, alone and in combination with 1,25-(OH)2D3, on the regulation of BGP mRNA levels in ROS 17/2 rat osteosarcoma cells. Elevation of intracellular cAMP levels by cAMP analogs or by isobutylmethylxanthine (IBMX), forskolin, or PTH, resulted in increased BGP mRNA levels and BGP secretion after 1 day of treatment. The effects of these agents were additive with 1,25-(OH)2D3 in stimulating BGP gene expression. After 4 days of treatment, pertussis toxin (PT) and 1,25-(OH)2D3 were synergistic in stimulating BGP mRNA, and the effect of PT could be mimicked by (Bu)2cAMP, IBMX, forskolin, cholera toxin, and to a lesser extent by PTH. The effect of 1-day treatment with cAMP alone and the synergistic effect with 1,25-(OH)2D3 on the stimulation of BGP mRNA were dependent on cell density, while basal and 1,25-(OH)2D3-stimulated synthesis were not. Cyclic AMP inhibited ROS 17/2 cell growth after 1 day of treatment, an effect that was also dependent on initial cell density. After 4 days of treatment, 1,25-(OH)2D3, cAMP, and PT all demonstrated inhibition of cell growth. When cells were treated with actinomycin D, both 1,25-(OH)2D3 and cAMP stimulation of BGP mRNA were blocked. In addition, neither agent was effective in enhancing BGP mRNA stability when prestimulated cells were exposed to actinomycin D.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Bone Gla protein messenger ribonucleic acid is regulated by both 1,25-dihydroxyvitamin D3 and 3',5'-cyclic adenosine monophosphate in rat osteosarcoma cells. 246 56

We examined mechanisms of down-regulation of PTH receptors and desensitization of the PTH-stimulated increase in intracellular cAMP in clonal rat osteosarcoma cells, ROS 17/2.8. ROS cells treated with 10 nM [Nle8,Nle18,Tyr34] bovine (b) PTH-(1-34) amide (NlePTH) for 3 days showed loss of specific PTH binding and PTH-stimulated cAMP accumulation to 10% of that in vehicle-treated control cells. Treatment of these cells with both 0.5 mM 8-bromo-cAMP (8-Br-cAMP) and 1 mM methylisobutylxanthine or 100 ng/ml cholera toxin for 3 days elicited no change in either of these responses. Treatment with 10 nM NlePTH for 3 days did not modify the cAMP accumulation stimulated by 30 microM forskolin or 1 micrograms/ml cholera toxin, indicating that agonist-specific desensitization of PTH-stimulated cAMP accumulation is not due to diminished activity of either the stimulatory guanyl nucleotide regulatory subunit (Gs) or the catalytic subunit of the adenylate cyclase. Treatment of ROS cells with pertussis toxin (PT; 10 ng/ml) for 12, 24, 48, and 72 h increased specific PTH binding by 21%, 28%, 35%, and 39%. The increase in PTH binding was associated with a parallel increase in PTH-stimulated cAMP accumulation and was due to an increase in the number of PTH receptors. PTH receptor affinity remained constant (apparent Kd = 0.3 nM). PT treatment of the cells partially blocked agonist-specific PTH receptor down-regulation. PT catalyzed ADP ribosylation of 41K and 39K membrane proteins, consistent with the alpha-subunits of Gi and Go, respectively. In conclusion, agonist-induced PTH receptor down-regulation in ROS 17/2.8 cells is cAMP independent and can be reversed by PT treatment. PTH receptor expression in these cells appears to be under tonic inhibitory control by mechanisms involving a PT-sensitive G protein(s).
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PMID:Inactivation of pertussis toxin-sensitive guanyl nucleotide-binding proteins increase parathyroid hormone receptors and reverse agonist-induced receptor down-regulation in ROS 17/2.8 cells. 247 33

Maitotoxin, a toxin derived from a marine dinoflagellate, is a potent activator of voltage-sensitive calcium channels. To further test the hypothesis that inhibition of PTH secretion by calcium is mediated via a calcium channel we studied the effect of maitotoxin on dispersed bovine parathyroid cells. Maitotoxin inhibited PTH release in a dose-dependent fashion, and inhibition was maximal at 1 ng/ml. Chelation of extracellular calcium by EGTA blocked the inhibition of PTH by maitotoxin. Maitotoxin enhanced the effects of the dihydropyridine calcium channel agonist (+)202-791 and increased the rate of radiocalcium uptake in parathyroid cells. Pertussis toxin, which ADP-ribosylates and inactivates a guanine nucleotide regulatory protein that interacts with calcium channels in the parathyroid cell, did not affect the inhibition of PTH secretion by maitotoxin. Maitotoxin, by its action on calcium channels allows entry of extracellular calcium and inhibits PTH release. Our results suggest that calcium channels are involved in the release of PTH. Inhibition of PTH release by maitotoxin is not sensitive to pertussis toxin, suggesting that maitotoxin may act distal to the site interacting with a guanine nucleotide regulatory protein, or maitotoxin could interact with other ions or second messengers to inhibit PTH release.
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PMID:Inhibition of parathyroid hormone release by maitotoxin, a calcium channel activator. 253 15

We tested the effects that pertussis toxin had on bone resorption mediated by cAMP-dependent and cAMP-independent stimuli in 19-day-old fetal rat long bones. Agents that stimulate cAMP were PTH, prostaglandin E2, and calcitonin. Agents that act independent of cAMP were: phorbol 13-myristate 12-acetate (PMA), 1,25-dihydroxyvitamin D3, murine interleukin-1 alpha, osteoclast-activating factor, and human tumor necrosis factor-alpha. Pertussis (1-10 ng/ml) produced a dose-related inhibition of resorption in unstimulated control cultures. The inhibitory effect was not associated with changes in either [3H]thymidine or [3H]proline incorporation into bones. beta-Glucuronidase activity in the medium was decreased. PMA was the only agonist whose resorptive effect was completely blocked by pertussis. The resorptive response to other stimulators was reduced, but treated/control ratios usually remained the same or increased because of the greater effect of pertussis on control resorption. There was a partial inhibition of the resorptive effect of low doses of prostaglandin E2 (10 nM), but increasing the concentration of agonist overcame the inhibition. Pertussis did not enhance the sensitivity of bones to calcitonin. Pertussis enhanced the cAMP response to PTH, but had no effect on basal cAMP production. Since PMA was inhibited by pertussis while agents that may act through cAMP-mediated or phosphatidylinositol pathways were not affected, we hypothesize that a protein kinase-C dependent pathway can modulate bone resorption.
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PMID:Effects of pertussis toxin on resorption of 19-day-old fetal rat long bones. 253 69


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