A transferrin-mediated uptake of gallium-67 by EMT-6 sarcoma. I. Studies in tissue culture.
We have studied the in vitro uptake of gallium-67 by exponentially growing EMT-6 sarcoma cells in long-term tissue culture. In this system, the addition of transferrin to the medium was required before an appreciable cellular uptake of Ga-67 occurred. The transferrin effect was complex, with an initial stimulation to a peak cell-to-medium ratio of 8--10:1 at low concentrations of transferrin (0.2 mg/ml), followed by a gradual decline in uptake as transferrin in the medium was increased further. EMT-6 tumor-cell uptake of Ga-67 was probably mediated by a specific cellular receptor for transferrin. Scatchard analysis of the EMT-6 cellular binding of human transferrin labeled with iodine-125 indicated a cellular receptor with affinity for transferrin of 5 X 10(6) l/mole and abundance of 500,000 receptors per cell. Over the experimental range of transferrin concentration in the medium, the observed uptake of Ga-67 was closely correlated with the degree of formation of Ga-67-labeled transferrin and the fraction of transferrin bound to the cellular receptor (N = 69, r = 0.86, p less than 0.0001).
D000818:Animals; D005708:Gallium / Q000378:metabolism; D005710:Gallium Radioisotopes; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D011955:Receptors, Drug / Q000378:metabolism; D012513:Sarcoma, Experimental / Q000378:metabolism*; D013268:Stimulation, Chemical; D014168:Transferrin / Q000378:metabolism / Q000494:pharmacology*
D005710:Gallium Radioisotopes; D011955:Receptors, Drug; D014168:Transferrin; D005708:Gallium