EXPRESSION OF FUNCTIONAL GROWTH-HORMONE RECEPTORS IN CULTURED HUMAN OSTEOBLAST-LIKE CELLS

Recent clinical studies indicate that GH is important for bone remodeling. Patients with GH deficiency exhibit decreased bone density, and GH substitution increases bone density in these patients. The aim of the present study was to investigate the presence of GH receptors and the effects of GH on cultured human osteoblast-like cells. Primary cultures of human osteoblast-like cells were established from trabecular bone. Northern blot analysis, using a probe recognizing exon 10 of the human GH receptor, revealed a 4.7-kilobase transcript corresponding to the human GH receptor. Cultured osteoblast-like cells expressed, as determined by RNase protection assay, approximately one fourth of the GH receptor messenger RNA levels found in liver. Binding studies using I-125-labeled GH revealed a single class of receptors with approximately 2000 binding sites per cell and an association constant (K-a) of 2.6 x 10(9) M(-1). GH stimulation of the cultured cells resulted in increased [H-3]thymidine incorporation, suggesting that the GH receptors are functional. In summary, the present study shows that cultured human osteoblast-like cells express functional GH receptors.