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), Journal Name: Endocrinology; (United States) Vol. 111:5; ISSN ENDOA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CELL CONSTITUENTS
CELL CULTURES
CELL MEMBRANES
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LEUKOCYTES
LYMPHOCYTES
MATERIALS
MEMBRANES
NUCLEI
ODD-EVEN NUCLEI
PEPTIDE HORMONES
PH VALUE
PHYSIOLOGY
PITUITARY HORMONES
RADIOISOTOPES
REACTION KINETICS
SOMATIC CELLS
STH
TEMPERATURE DEPENDENCE