Effect of 1,25(OH)2D3 on expression of estrogen receptor-alpha mRNA on rat osteosarcoma cell line (ROS 17/2.8)

In order to investigate the regulatory mechanisms of estrogen receptors (ER) in bone cells, changes in ER-alpha mRNA levels of rat osteosarcoma cell line (ROS 17/2.8) before and after exposure to 1,25(OH)2D3 and 17-beta estradiol respectively were measured by quantitative polymerase chain reaction using an internal standard. ER mRNA levels in the ROS 17/2.8 cultured with the medium alone had 5.029 +/- 1.623 mol/g total RNA x 10(-13) and were not statistically different from those cultured in the presence of 1,25(OH)2D3 at concentrations of 10(-12) M and less. ER mRNA levels in the ROS 17/2.8 cell line showed a small but a significant increase as a result of stimulation by 1,25(OH)2D3 at concentrations of 10(-10) and 10(-11) M. However, ER mRNA levels in ROS 17/2.8 cultured in the presence of 1,25(OH)2D3 at concentrations of 10(-9) M were not statistically different from those of the control. On the other hand, the expression of ER in ROS 17/2.8 cells cultured for 3 hours with various doses of 1,25(OH)2D3 showed, by immunoblotting methods, a significant increase at the dose of 10(-10) M in the expression of ER. Although a physiological significance is obscure, these observations suggest that 1,25(OH)2D3 plays a part in the expression of ER in ROS 17/2.8. No significant changes were seen in the expression of ER mRNA and the synthesis of ER as a result of stimulation by the estradiol.