Evaluation of an in Vitro Parathyroid Hormone Antagonist<i>in Vivo</i>in Dogs*

Segre, Gino V.; Rosenblatt, Michael; Tully, George L.; Laugharn, James; B, Reit; Potts, John T.

doi:10.1210/endo-116-3-1024

Cited by 37 publications

(9 citation statements)

References 17 publications

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“…These studies demonstrated partial agonist activity of the putative inhibitor in terms of cAMP production by bone. These observations are consistent with the report of Segre et al [22] who demonstrated agonist activity of this "inhibitory" peptide in vivo.…”

Section: Discussionsupporting

confidence: 93%

Relative sensitivity of kidney and bone to the amino-terminal fragment b-PTH (1–30) of native bovine parathyroid hormone: Implications for assessment of bioactivity of parathyroid hormone fragments in vivo and in vitro

et al. 1983

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Summary: Adenylate cyclase activation in renal cortical membranes is widely used to assess the potency of parathyroid hormone (PTH) and hormonal fragments. Recent studies, however, suggest that the structural requirements for biological activity of PTH in bone may differ from those in kidney. In isolated perfused canine bone, cyclic AMP production is markedly increased by syn-b-PTH (1-34) whereas intact b-PTH (1-84) has minimal effect. Furthermore, a potent inhibitor of PTH stimulated adenylate cyclase activity, NleSNle18Tyl ~4 syn-b-PTH (3-34) NH2, devoid of biological activity in kidney, is an agonist in isolated bone. The present studies examine the effects in bone and kidney of the amino-terminal fragment b-PTH (1-30), prepared by cleavage of intact b-PTH (1-84) by Cathepsin B in vitro. In basolateral canine renal cortical membranes, b-PTH (1-30) was less active than syn-b-PTH (1-34) in its ability to stimulate adenylate cyclase. Half maximal stimulation of adenylate cyclase activity by b-PTH (1-30) was 50 nM compared with 2 nM for syn-b-PTH (1-34). Maximum enzyme activation by b-PTH (1-30) reached only 50%, of the activation by syn-b-PTH (1-34). Addition of Gpp(NH)p (1 mM) increased the affinities for both peptides. The relative difference in potency, however, remained unchanged. In contrast, in isolated bone, b-PTH (1-30) and syn-b-PTH (l-34) were equipotent in increasing cyclic AMP production. These data provide further evidence for differences in the structural requirements for PTH activity in bone and kidney and suggest that bioassays of PTH and PTH fragments in kidney may not accurately reflect the effects of PTH in bone.

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Section: Discussionsupporting

confidence: 93%

Relative sensitivity of kidney and bone to the amino-terminal fragment b-PTH (1–30) of native bovine parathyroid hormone: Implications for assessment of bioactivity of parathyroid hormone fragments in vivo and in vitro

et al. 1983

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“…However, the receptor-binding region appears to be confined within residues 14-34 (Tregear, Rietschoten, Green, Keutmann, Niall, Reit, Parsons & Potts, 1973; Kronenberg & Rosenblatt, 1982;Segre, Rosenblatt, Tully, Laugharn, Reit & Potts, 1985). Similarly to PTH, PTHrP(I 34) in this study produced relaxation of the smooth muscle of the rat uterus in a dose-related manner.…”

Section: Discussionmentioning

confidence: 60%

The effects in the rat of two fragments of parathyroid hormone‐related protein on uterine contractions in situ

Barri

Abbas²,

Care³

1992

Experimental Physiology

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SUMMARYSynthetic parathyroid hormone fragment PTH(1-34) has been reported recently to inhibit uterine contractions stimulated by a variety of agonists. We have studied the effect in this system of the parathyroid hormone-related protein fragment PTHrP(I-34) which shows 60 % homology with PTH over the first thirteen amino acid residues. The effects of two different PTHrP fragments on acetylcholine-stimulated uterine contractions in vitro were studied. Whereas synthetic hPTHrP(75-86 amide) (10-9-10-7 M) was without effect, synthetic hPTHrP(I-34) (10-9-10-7 M) was capable of inhibiting, in a dose-related fashion, uterine muscle contractions precontracted with 10-6 M-acetylcholine. In a second series of experiments the bovine PTH(3-34) fragment itself was shown to have no stimulatory effect on acetylcholinestimulated contractions. Also this fragment in an equimolar concentration (10-7 M) failed to antagonize the effects of PTHrP(1-34) on acetylcholine-stimulated uterine contractions. However, a 100-fold excess molar concentration of bPTH(3-34) (10-6 M) completely abolished the inhibitory action of hPTHrP(I-34) (10-8 M) on acetylcholine-stimulated uterine contractions. These results clearly show that the inhibitory action of PTH(I-34) and PTHrP(I-34) on uterine contractions depends on the integrity of the amino-terminal region of the molecule.

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“…This differ¬ ence may be related to differences in magnitude of agonist effects, which are 50-to 100-fold in the intact cells, and 3-to 5-fold in membranes. In studies with intact PTH-responsive cells (Goldring et al 1979), inhibition of bPTH response approached 100% when (Nle8,Nle18,Tyr34)bPTH(3-34) amide was used as antagonist but, as previously noted, this analogue has significant agonist effect in vivo (Segre et al 1985).…”

Section: Discussionmentioning

confidence: 82%

Efficacy and specificity of human parathyroid hormone analogues as antagonists in intact clonal osteogenic sarcoma cells

Kubota¹,

Ng²,

Murase³

et al. 1986

Journal of Endocrinology

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Five synthetic analogues of human parathyroid hormone (hPTH), (Tyr34)hPTH(3-34) amide, (5-34) amide, (7-34) amide, (8-34) amide and (9-34) amide, were tested for their ability to antagonize hPTH action specifically in intact cultured cells. Clonal rat osteogenic sarcoma cells were used (UMR 106-06 line) which respond to PTH with an increase in cyclic AMP (cAMP) formation. The most potent antagonists were (Tyr34)hPTH(3-34) amide and (5-34) amide, which inhibited the effect of hPTH(2.4 nmol/l) with half maximally effective concentrations of 0.1 mumol/l. When conditioned medium was used from a human lung cancer cell line producing osteoblast adenylate cyclase-stimulating activity, these two analogues were capable of inhibiting the increase in cAMP production. The specificity of the antagonism was indicated by the inability of the analogues to influence the effects of prostaglandin E2 or of calcitonin, which are alternative stimulators of cAMP production in the osteogenic sarcoma cells. Only (Tyr34)hPTH(3-34) amide showed some PTH-like agonist activity at high concentrations. These analogues should prove valuable in the investigation of PTH actions on target cells and of tumour products which appear to act through the PTH receptor.

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Evaluation of an in Vitro Parathyroid Hormone Antagonistin Vivoin Dogs*

Cited by 37 publications

References 17 publications

Relative sensitivity of kidney and bone to the amino-terminal fragment b-PTH (1–30) of native bovine parathyroid hormone: Implications for assessment of bioactivity of parathyroid hormone fragments in vivo and in vitro

Relative sensitivity of kidney and bone to the amino-terminal fragment b-PTH (1–30) of native bovine parathyroid hormone: Implications for assessment of bioactivity of parathyroid hormone fragments in vivo and in vitro

The effects in the rat of two fragments of parathyroid hormone‐related protein on uterine contractions in situ

Efficacy and specificity of human parathyroid hormone analogues as antagonists in intact clonal osteogenic sarcoma cells

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