CARBOXYL-TERMINAL PARATHYROID-HORMONE PEPTIDE (53-84) ELEVATES ALKALINE-PHOSPHATASE AND OSTEOCALCIN MESSENGER-RNA LEVELS IN SAOS-2 CELLS

Previous findings in our laboratory have shown that hPTH-(53-84) stimu lates alkaline phosphatase activity in dexamethasone-treated ROS 17/2. 8 cells. In the present study, we examined the effects of hPTH-(53-84) and hPTH-(1-34) on the expressions of alkaline phosphatase, osteocalc in, and collagen type 1 mRNA levels in the human osteosarcoma cell lin e SaOS-2. The effect of hPTH-(53-84) on alkaline phosphatase and osteo calcin message levels was dose dependent (ANOVA, p < 0.005 and p < 0.0 01, respectively), with significant stimulation observed at 10 nM. Tre atment with 10 nM hPTH-(53-84) for 24 h resulted in significant 2- and 1.4-fold increases in mRNA levels for alkaline phosphatase and osteoc alcin, respectively (p < 0.05), but had no effect on collagen type I e xpression. The increased alkaline phosphatase mRNA levels was associat ed with a 1.5-fold increase in enzyme activity (p < 0.05). In contrast , under similar incubation conditions, hPTH-(1-34) had no significant effects on alkaline phosphatase or osteocalcin mRNA levels. On the oth er hand, hPTH-(1-34) had dose-dependent stimulatory effects on collage n type I mRNA levels (ANOVA, p < 0.001), 10 nM hPTH-(1-34) stimulating collagen type I expression 1.6-fold (p < 0.05). The results indicate that carboxyl-terminal hPTH-(53-84) has direct and unique biologic eff ects in human osteoblast-like cells in culture.