Extracellular Ca2+ sensing by the osteoblast-like cell line, MC3T3-E1

The present study was undertaken to clarify the role of extracellular calcium on osteoblast activation. It was found that bradykinin and thrombin induced synthesis of prostaglandin E2 was strongly dependent on the concentration of extracellular calcium in the osteoblast-like cell line, MC3T3-E1. Moreover, this effect was not related to Ca2+ influx, since it was even potentiated by Ni2+ and Co2+, which was not due to intracellular activity of Ni2+, as judged by studies with 63Ni2+. Ba2+, Mg2+ and Sr2+ had no effect. Cd2+ caused dose-dependent synthesis of prostaglandin E2, which was shown to correlate with its cytotoxic properties. The results thus strongly suggest the presence of a divalent cation sensor in osteoblast-like MC3T3-E1 cells.