Carboxyl-terminal parathyroid hormone peptide (53–84) elevates alkaline phosphatase and osteocalcin mRNA levels in SaOS-2 cells

Abstract

Previous findings in our laboratory have shown that hPTH‐(53–84) stimulates 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, osteocalcin, and collagen type I mRNA levels in the human osteosarcoma cell line SaOS‐2. The effect of hPTH‐(53–84) on alkaline phosphatase and osteocalcin message levels was dose dependent (ANOVA, p < 0.005 and p < 0.001, respectively), with significant stimulation observed at 10 nM. Treatment 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 osteocalcin, respectively (p < 0.05), but had no effect on collagen type I expression. The increased alkaline phosphatase mRNA levels was associated 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 other hand, hPTH‐(1–34) had dose‐dependent stimulatory effects on collagen 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 effects in human osteoblast‐like cells in culture.