ABSTRACT
A positron-emitting isotope of bromine, 76Br, with a half-life of 16.2 h, was produced using the reaction natBr(p, xn)76Kr. Labelling of mouse epidermal growth factor (EGF) with 76Br was optimized, using the chloramine-T method, obtaining a maximal radiochemical yield of 53%. In tests with receptor-rich, cultured glioma cells, [76Br]EGF and [125I]EGF bound equally well. A study of the distribution and stability of [76Br]EGF and [125I]EGF in normal rat was carried out. The distribution of both radioisotopes was similar, however, the percentage of 76Br bound to the high molecular weight fraction in the plasma, liver and kidney was greater than that of 125I.
Subject(s)
Bromine Radioisotopes/pharmacokinetics , Epidermal Growth Factor/pharmacokinetics , Iodine Radioisotopes/pharmacokinetics , Animals , Drug Stability , Isotope Labeling , Male , Rats , Rats, Inbred Strains , Tissue DistributionABSTRACT
A generator system, 110Sn/110In, is suggested for use in the labelling of leukocytes with this short-lived (t1/2 = 1.15 h) positron emitting (62%) isotope of indium. The half-life gives the labelled leukocytes time to be adequately distributed but is short enough to allow repeated studies within a few hours. The mother radionuclide 110Sn (t1/2 = 4.15 h) is produced by the reaction natIn(p, xn)110Sn which has a maximum cross-section of 110 mb at approx. 70 MeV and a practical yield of 400 MBq/microAh.
Subject(s)
Indium Radioisotopes , Radionuclide Generators , Tomography, Emission-Computed , Isotope Labeling/instrumentation , Leukocytes , Tin RadioisotopesABSTRACT
Malignant glioma cells often have more epidermal growth factor (EGF) receptors than normal cells and targeting of toxic substances to the receptor might therefore be an attractive therapeutical approach. Radiation effects were analysed on human glioma cells growing as monolayers after exposure to 131I-EGF. Unspecific effects were analysed with 131I-BSA or after presaturation with nonradioactive EGF. The radiation effects were compared to the effects obtained by external 60Co gamma irradiation. Administration of the highest radioactive concentrations, 0.2-0.5 MBq/ml in the culture medium, corresponded, after 20 min incubation, to a binding of about 1.0-2.5 dpm/cell. Such an exposure to 131I decays gave effects on cell survival corresponding to about 2.5 Gy of external gamma irradiation. Somewhat less than half of this effect came from the specific bound radioactivity and the rest from nonbound radioactivity. When administrating lower concentrations of radioactivity both the binding and the radiation effects were smaller. The observations showed that it is possible to inactivate cell-proliferation of glioma cells with specific bound 131I-EGF. The possibilities to fractionate the treatments and of binding also other toxic agents than 131I to the EGF receptor are discussed.
