OBJECTIVETo observe the effects of different human parathyroid hormone 1-34 (hPTH1-34) administration on SaoS-2 cells, and explore the mechanism of bone formation improvement.

METHODSEach cycle covered 48 h. SaoS-2 cells were continuously or intermittently stimulated by 50 ng/ml hPTH1-34 for 1, 3, 6, 12, and 24 h in each cycle. Total RNA was extracted by Trizol kit. Alkaline phosphatase (ALP), osteocalcin or bone Gla-containing protein (BGP) and cyclic adenosine monophosphate (cAMP) levels were measured by chemical method, radioimmunoassay and competitive protein binding method, respectively. c-fos gene expression was semi-quantified by reverse transcription polymerase chain reaction (RT-PCR).

RESULTSALP level was time-dependently increased in 1, 3 and 6 h stimulation, especially in 3 and 6 h (compared with control, P < 0.01; P < 0.05 or P < 0.01 compared with continuous stimulation). The cAMP level was time-dependently increased in 3 and 6 h incubation (P < 0.05 compared with control and continuous stimulation). Intermittent hPTH1-34 stimulation had more effects on cAMP level than continous action (P < 0.001). hPTH1-34 intermittent stimulation of 1, 3, and 6 h enhanced c-fos gene expression time-dependently.

CONCLUSIONSIntermittent hPTH1-34 stimulation has a stronger effect on osteoblast than continuous action, especially in 3, 6 h in each cycle intermittent stimulation. The synchronous responses of c-fos, ALP and cAMP to hPTH1-34 suggest that hPTH1-34 affect Saos-2 cells through cAMP dependent protein kinase A (PKA) pathway and c-fos gene paly an important role.