Receptor-mediated degradation of human growth hormone in rat adipocytes and cultured human lymphocytes (IM-9).

In cultured human lymphocytes (IM-9) and in isolated rat adipocytes human growth hormone is substrate for a receptor-mediated degradation. When the cells are incubated with monoiodinated human growth hormone half of the radioactivity dissociating from the cells is in the form of [125I]monoiodotyrosine. Since IM-9 lymphocytes have no receptor-mediated degradation of insulin, obviously insulin and human growth hormone follow different pathways in this cell type. In the rat adipocyte colchicine and monodansylcadaverine caused quantitatively different uptake and degradation of these 2 ligands suggesting that also in this cell type the pathways are functionally different. The application of different inhibitors suggests that the receptor-mediated degradation of growth hormone in these 2 cell types takes place in an acidified compartment by an energy-requiring process and involving thiol groups.