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Parathyroid Hormone (PTH)-(1–34),[ Nle 8,18 ,Tyr 34 ]PTH-(3–34) Amide, PTH-(1–31) Amide, and PTH-Related Peptide-(1–34) Stimulate Phosphatidylcholine Hydrolysis in UMR-106 Osteoblastic Cells: Comparison with Effects of Phorbol 12,13-Dibutyrate 1

1999; Oxford University Press; Volume: 140; Issue: 1 Linguagem: Inglês

10.1210/endo.140.1.6456

1945-7170

Amareshwar T.K. Singh, Joseph G. Kunnel, Paul J. Strieleman, Paula H. Stern,

Protein Kinase Regulation and GTPase Signaling

Studies were performed to determine the effects of PTH and related compounds on phosphatidylcholine (PC) hydrolysis in UMR-106 cells and the pathway by which the PTH effects occurred. The responses were compared with those of phorbol 12,13-dibutyrate (PDBu). Both bovine PTH-(1–34) [bPTH-(1–34)] and PDBu stimulated PC hydrolysis within 10 min. Significant effects were elicited by concentrations of 0.3–1 nm bPTH-(1–34) and 5 nm PDBu. Dose-dependent increases were seen at higher concentrations of both compounds, however, the response to bPTH-(1–34) was reduced at 30 nm. Bovine or human PTH-(1–34) and human PTH-related peptide-(1–34)[ hPTHrP-(1–34)] were equipotent in their effects, whereas bovine[ Nle8,18Tyr34]PTH-(3–34) amide[ bPTH-(3–34)] and hPTH-(1–31) amide [hPTH-(1–31)] were less potent than bPTH-(1–34). bPTH-(3–34) did not antagonize the effects of bPTH-(1–34). Down-regulation of protein kinase C isozymes by 24-h treatment with PDBu completely prevented the stimulatory effect of PDBu on PC hydrolysis, but did not significantly affect the stimulatory effect of bPTH-(1–34). Both bPTH-(1–34) and PDBu stimulated transphosphatidylation of PC, indicating a phospholipase D-stimulated mechanism. The results suggest that in the UMR-106 cell line PTH can stimulate activation of PLD by a mechanism other than through protein kinase C.