Molecular characterization of the alpha1 subunit of the L type voltage calcium channel expressed in rat calvarial osteoblasts.
A low concentration of boron (B) accelerates the proliferation and differentiation of mammalian osteoblasts. The aim of this study was to investigate the effects of 0.1 mM of B on the membrane function of osteoblastic cells in vitro. Genes involved in cell activity were investigated using gene expression microarray analyses. The Ca2+ influx and efflux were evaluated to demonstrate the activation of L-type Ca2+ channel for the Ca2+ influx, and that of Na+/K+-ATPase for the Ca2+ efflux. A real-time PCR analysis revealed that the messenger RNA (mRNA) expression of four mineralization-related genes was clearly increased after 3 days of culture with a B-supplemented culture medium. Using microarray analyses, five genes involved in cell proliferation and differentiation were upregulated compared to the control group. Regarding the Ca2+ influx, in the nifedipine-pretreated group, the relative fluorescence intensity for 1 min after adding B solution did not increase compared with that for 1 min before addition. In the control group, the relative fluorescence intensity was significantly increased compared with the experimental group (P < 0.05). Regarding the Ca2+ efflux, in the experimental group cultured in 0.1 mM of B-supplemented medium, the relative fluorescence intensity for 10 min after ouabain treatment revealed a significantly lower slope value compared with the control group (P < 0.01). This is the first study to demonstrate the acceleration of Ca2+ flux by B supplementation in osteoblastic cells. Cell membrane stability is related to the mechanism by which a very low concentration of B promotes the proliferation and differentiation of mammalian osteoblastic cells in vitro.