Effect of lead on apoptosis in cultured rat primary osteoblasts

To investigate the effect of lead exposure on apoptosis of cultured rat primary osteoblasts (ROBs), which were derived from newborn calvariae of Sprague Dawley rat. They were identified by the staining of alkaline phosphatase and mineralized matrix. The ROBs were received at 0, 20, 40 and 80 μM Pb2+ of lead acetate solution for 24 h, respectively, before being doubly marked by Annexin V-fluorescein isothiocyanate/propidium iodide. The intracellular concentration of calcium ([Ca2+](i)) was detected under the laser scan confocal microscope. The activities of phosphatidylcholine-specific phospholipase C (PC-PLC) were measured and the effect of lead exposure on the expression of PC-PLC was observed by immunoblotting assay. The results showed that when compared with that of the control group, lead exposure induced an increase of [Ca2+](i) of lead-treated ROBs, resulting in a significant development in apoptosis. In the meantime, a significant decline in protein level and enzymatic activities of PC-PLC were observed in a dose-dependent manner. It was concluded that lead can induce apoptosis in ROBs, and one of the mechanisms of lead-induced apoptosis may be that activating intracellular calcium stores by decreasing protein levels and enzymatic activities of PC-PLC can increase the [Ca2+](i), and consequently, the apoptotic signal pathway can be induced.