A Preliminary Study On The Molecular Mechanism Of The Effects Of PTH On Rat Osteoblast

Objective: Parathyroid hormone is one of the most important hormones that could regulate bone metabolism. In the patients of hyperparathyroidism, the serum calcium level increased and the bone resorption increased, finally osteoporosis could be seen in this kind of patients. However, on the other hand, intermittent PTH treatment at low dosage will increase bone formation. So PTH is considered as the only drug that can cure osteoporosis. Although the biphasic effects of PTH on bone formation is always a hot point, the mechanism remained unclear. To investigate the mechanism of biphasic effects of PTH on bone metabolism, the related cytokines expression were detected in the rat osteoblast under different PTH treatment conditions.Methods: Osteoblasts were isolated from new-born rat calvariae by gradually trypsin digestion process and cultured in DMEM/F12 culture medium. The cells of the third to fifth passage were plated in 96-well, 24-well and 12-well plates and treated with PTH. There were three groups. [1] Control, the cells were cultured without PTH. [2] Intermittent exposure to PTH, the cells were cultured with PTH during the first 6 hours, but without PTH in the subsequent 42 hours; and [3] Continuous exposure to PTH, the cells were cultured with PTH during the first 6 hours and the subsequent 42 hours. Every 48 hours was considered as a cycle. At the first to eight cycles finished the cells were harvested to measure MTT value, ALP activity and RNA was isolated. mRNA level of BMP-2, IGF-1, RANKL and OPG were determined by quantitative real-time RT-PCR. Results: MTT results showed cell proliferation of ROB were increased in...