Binding, internalization, and lysosomal association of 125I-human growth hormone in cultured human lymphocytes: a quantitative morphological and biochemical study.

摘要: 125I-human growth hormone (125I-hGH) binds specifically to receptors on cultures human lymphocytes (IM-9). When this process is studied by use of quantitative EM radioautography, under conditions incubation at 15 degrees C for 5 min, the ligand localized plasma membrane cell. At 30 and 37 C, however, 125I-hGH progressively internalized cell as a function time. The found predominantly in Golgi region cells, with five-fold preferential localization membrane-bounded structures morphological cytochemical characteristics lysosomes. Up 59% these lysosome-like are positive acid phosphatase reaction 120 min. associated radioactivity after 15-120 min extracted 1 M acetic filtered Sephadex G-100 column, 58-73% material elutes intact hGH. cells incubated separated from medium, washed diluted 100-fold, percent dissociable decreases increasing time incubation. that dissociates during 15-90 studied, labeled appearing medium degraded dissociation radioautographically, grains both intracelluar compartments association, but higher proportion intracellular compartment. After there less either compartment increase These data suggest receptor-linked internalization polypeptide provides mechanism couples degradation loss surface receptor.