Specific binding of phorbol esters to Friend erythroleukemia cells--general properties, down regulation and relationship to cell differentiation
Specific and saturable binding sites for (20-/sup 3/H)phorbol 12,13-dibutyrate ((/sup 3/H)PDBu) were demonstrated in tact Friend erythroleukemia cells (FELC), in which inducible erythroid differentiation is reversibly inhibited by phorbol esters. The binding of (/sup 3/H)PDBu to intact cells was maximal within only 15 min of incubation at 37 degrees C, after which there was a gradual decrease; binding at 4 degrees C however, was alow process, requiring greater than 180 min for maximal binding. A Scatchard analysis showed that the dissociation constant for binding of (/sup 3/H)PDBu is 8.3 nM; at saturation, approximately 1.75 x 10(5) molecules of (/sup 3/H)PDBu are bound per cell. When FELC were induced to differentiate with 4mM hexameethylene bisacetamide (approximately 80% of cells were benzidine-positive), a slight decrease (10-20%) in the number of binding sites at saturation was seen, but the dissociation constant was not changed. When the cells were precultured with non-radioactive phorbol esters, a significant decrease in (/sup 3/H)PDBu binding was observed, suggesting a homologous down regulation of phorbol ester receptors. Scatchard analysis indicated that the decrease in (/sup 3/H)PDBu binding was due to a decrease in the number of binding sites and not to a change in affinity. Such specific phorbol ester binding sites might mediate a number of biochemical and biological effects of phorbol esters on FELC.
- Research Organization:
- International Agency for Research on Cancer, Lyon Cedex, France
- OSTI ID:
- 6564576
- Journal Information:
- Carcinogenesis (N.Y.); (United States), Vol. 3:8
- Country of Publication:
- United States
- Language:
- English
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ERYTHROCYTES
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RECEPTORS
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TRACER TECHNIQUES
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LEUKEMIA
TEMPERATURE DEPENDENCE
BIOLOGICAL MATERIALS
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BLOOD CELLS
BODY FLUIDS
CARCINOGENS
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