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

Recent clinical studies indicate that GH is important for bone remodel ing. Patients with GH deficiency exhibit decreased bone density, and G H substitution increases bone density in these patients. The aim of th e present study was to investigate the presence of GH receptors and th e effects of GH on cultured human osteoblast-like cells. Primary cultu res of human osteoblast-like cells were established from trabecular bo ne. Northern blot analysis, using a probe recognizing exon 10 of the h uman GH receptor, revealed a 4.7-kilobase transcript corresponding to the human GH receptor. Cultured osteoblast-like cells expressed, as de termined 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 approximatel y 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 incre ased [H-3]thymidine incorporation, suggesting that the GH receptors ar e functional. In summary, the present study shows that cultured human osteoblast-like cells express functional GH receptors.