Thyroid Hormone Receptors In Bone And Osteoblasts

To study the function of thyroid hormone receptors (TRs) in osteoblasts and in bone, the nuclear extracts of TRs from human osteoblast-like cell line MG63 and rat calvaria were achieved, and the two main kinetic parameters of TRs, affinity constant (Ka) and maximal binding capacity (MBC), were determined by radio-ligand binding assay (RLBA) and Scatchard plot. The high-affinity binding of ~125I-triiodothyronirie to the nuclear extracts was demonstrated, and Ka of TRs in MG63 cell line and in rat calvaria were 7.68±1.96×l0~9L/mol and 5.33±0.31×l0~9L/mol, MBC were 111.3±10.7fmol/mg pro and 743.1±98.3fmol/mg pro, respectively. The data indicate that the binding of triiodothyronine to the TRs in osteoblasts and in bone might be less than that in brain and liver, and the mechanism of THs function in bone could be some different from that in other tissues. The method had been successful developed for analyzing the kinetics of TRs in bone and satisfied results obtained. It is important for the further investigation of TRs in vivo.