Objective To clarify the influence of Ca and P on bone metabolism by investigating theeir effects on proliferation, differentiation and mineralization of osteoblasts (OBs) in vitro. Method OBs were cultured in media with Ca(1, 2,4 mmol/L),P(1, 2,4 mmol/L),Ca:P 1:2 (1 mmol/L Ca+2 mmol/L P), and Ca:P 2:1 (2 mmol/L Ca+1 mmol/L P). Cell proliferation, activity of alkaline phosphatase (ALP), content of osteopontin (OPN) and collagen type I (Col-I) of OBs, and their corresponding mRNA expression were measured. Results Compared with control group,Ca at 4 mmol/L promoted OBs proliferation significanty (P

Objective To study the effect of 1?,25-dihydroxyvitamin D3[1,25-(OH)2D3] on cytoskeleton,gap junction intercellular communication (GJIC) and intracellular Ca2+ ([Ca2+]i) in osteoblasts (OB) in vitro. Method OB were isolated from calvaria bone. After 20 min and after 24 h treated by 1,25-(OH)2 VD3 (0,10-9,10-8,10-7 mol/L),[Ca2+]i was evaluated. F-actin and GJIC were observed after 24 and 48 h incubation later. Results Compared with the control group,[Ca2+]i in all 1,25-(OH)2 D3 groups was increased significantly at 20 min. [Ca2+]i in 10-9 mol/L 1,25-(OH)2D3 group was the lowest at 24 h after treatment. OB in 10-8 and 10-7 mol/L 1,25-(OH)2D3 groups were flat,and stress fibers were formed. The expression of F-actin in control group and 10-9 mol/L 1,25-(OH)2D3 group was reduced at 48 h after treatment. Compared with the control group,GJIC was weakened very significantly after treated with 10-9 mol/L 1,25-(OH)2D3 at 48 h,but enhanced very significantly in the group with 10-8 and 10-7 mol/L. Conclusion Higher dosage of 1,25-(OH)2D3 can maintain the morphology of OB and stimulate the communication among OB,but lower dosage can inhibit it.

Gap junctions mediate direct communication between cells; however, toxicological cascade triggered by nonessential metals can abrogate cellular signaling mediated by gap junctions. Although cadmium (Cd) is known to induce apoptosis in organs and tissues, the mechanisms that underlie gap junction activity in Cd-induced apoptosis in BRL 3A rat liver cells has yet to be established. In this study, we showed that Cd treatment decreased the cell index (a measure of cellular electrical impedance) in BRL 3A cells. Mechanistically, we found that Cd exposure decreased expression of connexin 43 (Cx43), increased expression of p-Cx43 and elevated intracellular free Ca2+ concentration, corresponding to a decrease in gap junctional intercellular communication. Gap junction blockage pretreatment with 18β-glycyrrhizic acid (GA) promoted Cd-induced apoptosis, involving changes in expression of Bax, Bcl-2, caspase-3 and the mitochondrial transmembrane electrical potential (Δψm). Additionally, GA was found to enhance ERK and p38 activation during Cd-induced activation of mitogen-activated protein kinases, but had no significant effect on JNK activation. Our results indicated the apoptosis-related proteins and the ERK and p38 signaling pathways may participate in gap junction blockage promoting Cd-induced apoptosis in BRL 3A cells.
Animals ; Apoptosis/*drug effects ; Cadmium/*toxicity ; Calcium/metabolism ; Cell Communication/drug effects ; Connexin 43/genetics ; Enzyme Activation/drug effects ; Gap Junctions/*drug effects ; Gene Expression Regulation/drug effects ; Hepatocytes/cytology/*drug effects ; Rats ; Signal Transduction/drug effects