title: Stimulation of osteoblast proliferation by C-terminal fragments of parathyroid hormone-related protein.
abstract: Parathyroid hormone (PTH)-related protein (107-139) (PTHrP(107-139)) and PTHrP(107-111) have been reported to be potent inhibitors of isolated osteoclast activity, and inhibition of bone resorption by PTHrP(107-139) occurs in vivo. However, the actions of C-terminal PTHrP on osteoblast activity has not been studied much. The present study addresses this issue by examining the effect of PTHrP(107-139), PTHrP(107-119), PTHrP(120-139), and PTHrP(107-111) on the proliferation of fetal rat osteoblasts. Treatment with PTHrP(107-139) for 24 h caused a dose-dependent increase in cell number, [3H]thymidine and [3H]phenylalanine incorporation in cultured osteoblasts. The effect was apparent at concentrations of 10-10 M and greater and was sustained over time. PTHrP(107-119) and PTHrP(107-111) had effects on cell number, DNA, and protein synthesis which were comparable to those of PTHrP(107-139), whereas PTHrP(120-139) was without effect. Retroverted PTHrP(107-111) also stimulated all three activities but was only one tenth as potent as PTHrP(107-139). PTHrP(107-139) had no effect on osteoblast apoptosis. It is concluded that PTHrP(107-139) is not only an inhibitor of osteoclastic bone resorption but that it also stimulates osteoblast growth. This activity resides within the pentapeptide fragment PTHrP(107-111). These findings support a possible role for C-terminal fragments of PTHrP in the normal regulation of bone cell function and, possibly, bone mass.
authors.affiliation: Department of Medicine, University of Auckland, Auckland, New Zealand.
authors.forename: J
authors.initials: J
authors.lastname: Cornish
authors.forename: K E
authors.initials: KE
authors.lastname: Callon
authors.forename: C
authors.initials: C
authors.lastname: Lin
authors.forename: C
authors.initials: C
authors.lastname: Xiao
authors.forename: J M
authors.initials: JM
authors.lastname: Moseley
authors.forename: I R
authors.initials: IR
authors.lastname: Reid
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects*; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000494:pharmacology*; D011506:Proteins / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D013268:Stimulation, Chemical
chemical_list: D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins