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.