Effect of pH and lysosomotropic agents on membrane-associated and internalized /sup 125/I-iodinated human growth hormone in cultured human lymphocytes: a quantitative biochemical and electron microscopic study
When /sup 125/I-iodinated human GH ((/sup 125/I)iodo-hGH) interacts with cultured human lymphocytes at 15 C, the reaction is reversible, but at 37 C the reaction becomes less dissociable as a function of incubation time. Acidification of the incubation medium results in rapid ligand dissociation at 15 C, but at 37 C the acid-dissociable component decreases as a function of incubation time. Under conditions where approximately 50% of the ligand is internalized by the cell, 90% is nondissociable. When the 37 C incubation is carried out in the presence of 25 mM NH/sub 4/Cl, cell-associated radioactivity is increased. Under these conditions approximately 90% of cell-associated radioactivity also is nondissociable. Using quantitative electron microscopic autoradiography, the proportion of (/sup 125/I)iodo-hGH associated with the plasma membrane and internalized by the cell is indistinguishable in the presence or absence of NH/sub 4/Cl. Irreversible (/sup 125/I)iodo-hGH association with cultured human lymphocytes is due to time- and temperature-dependent effects in the plasma membrane of the cell. These effects cannot be distinguished from internalization by acidification. Furthermore, lysosomotropic agents increase cell-associated radioactivity, but the proportion internalized is not increased.
- Research Organization:
- Diabetes Branch, National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
- OSTI ID:
- 6493069
- Journal Information:
- Endocrinology; (United States), Vol. 111:5
- Country of Publication:
- United States
- Language:
- English
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PH VALUE
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ANIMAL CELLS
BETA DECAY RADIOISOTOPES
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550201* - Biochemistry- Tracer Techniques
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551001 - Physiological Systems- Tracer Techniques