title: Human parathyroid hormone (PTH)-related protein and human PTH: comparative biological activities on human bone cells and bone resorption.
abstract: Human PTH-related protein (hPTHrP) has been characterized as a product of tumor cells with sequence homology to the biologically active amino-terminal portion of human PTH (hPTH). We measured the relative activities of synthetic amino-terminal sequences of hPTH-(1-34) and hPTHrP-(1-34) to stimulate production of cAMP in intact human SaOS-2 osteosarcoma cells. Both peptides enhanced cAMP production at concentrations of 2.5-7.5 X 10(-10) M, had parallel dose-response curves, and were of essentially equal potency. Preincubation of SaOS-2 cells with hPTH-(1-34) or hPTHrP-(1-34) for 1 or 4 h induced homologous desensitization to a second challenge with the same peptide as well as heterologous desensitization to the other PTH peptide, but had little or no effect on the action of vasoactive intestinal peptide; the magnitudes of homologous and heterologous desensitization induced by the same doses of hPTHrP-(1-34) or hPTH-(1-34) were similar. Bone resorption-stimulating activity was measured using 40Ca2+ release from neonatal mouse calvariae in organ culture after 72 h of incubation. hPTHrP-(1-34) gave a dose-response between 0.2 and 5 ng/ml (5 X 10(-11) and 1.2 X 10(-9) M), was about 3 times more potent than Lilly bovine PTH standard (assuming a SA of 3000 U/mg; 100 U/ml), gave the same maximum response as hPTH-(1-34), and was 20-30% as potent as hPTH-(1-34). Neither hPTH-(1-34) nor hPTHrP-(1-34) enhanced prostaglandin production in mouse calvariae, and indomethacin did not inhibit the bone resorption-stimulating activities of either peptide. We conclude that hPTHrP-(1-34) and hPTH-(1-34) have similar high specific biological activities to stimulate production of cAMP in human osteoblast-like cells, but that hPTHrP-(1-34) is modestly less potent than hPTH-(1-34) to stimulate bone resorption in mouse calvariae.
authors.affiliation: Laboratory of Toxicology, Harvard School of Public Health, Boston, Massachusetts 02115.
authors.forename: S
authors.initials: S
authors.lastname: Fukayama
authors.forename: T J
authors.initials: TJ
authors.lastname: Bosma
authors.forename: D L
authors.initials: DL
authors.lastname: Goad
authors.forename: E F
authors.initials: EF
authors.lastname: Voelkel
authors.forename: A H
authors.initials: AH
authors.lastname: Tashjian
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D001862:Bone Resorption / Q000187:drug effects*; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D015232:Dinoprostone / Q000096:biosynthesis; D006801:Humans; D051379:Mice; D009363:Neoplasm Proteins / Q000494:pharmacology*; D009924:Organ Culture Techniques; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000494:pharmacology*; D011506:Proteins; D019379:Teriparatide; D014407:Tumor Cells, Cultured; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D009363:Neoplasm Proteins; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; D019379:Teriparatide; C054296:parathyroid hormone-related protein (1-34); D014660:Vasoactive Intestinal Peptide; D000242:Cyclic AMP; D015232:Dinoprostone; D002118:Calcium