title: Alteration of gallium-67 distribution in tumor-bearing mice following treatment with methotrexate: concise communication.
abstract: The effect of methotrexate (MTX) treatment upon Ga-67 distribution was investigated. Tumor bearing mice were injected with Ga-67 citrate at varying time intervals following MTX treatment administered either as a single dose or in multiple doses. Altered Ga-67 distribution was observed following MTX therapy, the general pattern showing decreased levels in blood and increased uptake in bone. MTX therapy decreased Ga-67 uptake in liver, tumor, and muscle. The effects of MTX are related to the dose and time interval between the administrations of MTX and Ga-67. The serum of MTX-treated mice had lower unsaturated iron-binding capacities and higher levels of unbound Ga-67. Serum iron and iron binding in rats determined 20 hr after MTX therapy showed significantly higher levels of serum iron and lower levels of Ga-67 in blood, and the percent transferrin saturation was approximately 95%. These observations suggest that MTX inhibition of erythropoiesis elevates serum iron levels and decreases the availability of gallium-binding sites in serum, resulting in altered Ga-67 tissue distribution.
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004920:Erythropoiesis / Q000187:drug effects; D005260:Female; D005710:Gallium Radioisotopes / Q000378:metabolism*; D007501:Iron / Q000097:blood; D008325:Mammary Neoplasms, Experimental / Q000000981:diagnostic imaging / Q000188:drug therapy*; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D008809:Mice, Inbred C3H; D009368:Neoplasm Transplantation; D011485:Protein Binding; D011877:Radionuclide Imaging; D051381:Rats; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D005710:Gallium Radioisotopes; D007501:Iron; D008727:Methotrexate