title: An optimized method for measuring cyclosporin A with 125I-labeled cyclosporin.
abstract: We evaluated the use of the new iodinated ligand for the in vitro measurement of cyclosporin A by radioimmunoassay (RIA). Substitution of the iodinated cyclosporin (125I-CyA) for the corresponding tritium-labeled analog (3H-CyA) considerably simplifies and accelerates the currently available RIA, and improves its precision. Analysis of the respective dose-response curves showed that the 50% B0 value was lower for the 125I-CyA assay than for the 3H-CyA assay (37 vs 77 micrograms/L). Use of whole-blood specimens minimized interferences from temperature and hematocrit. We conclude that the use of 125I-CyA in a commercially available RIA for whole-blood specimens is accessible to most laboratories and provides rapid, reproducible data for management of transplant patients.
mesh_terms: D003201:Computers; D003524:Cyclosporins / Q000097:blood* / Q000592:standards; D006400:Hematocrit; D006801:Humans; D007457:Iodine Radioisotopes; D016030:Kidney Transplantation; D011786:Quality Control; D011863:Radioimmunoassay / Q000379:methods; D011933:Reagent Kits, Diagnostic; D013223:Statistics as Topic; D014316:Tritium
chemical_list: D003524:Cyclosporins; D007457:Iodine Radioisotopes; D011933:Reagent Kits, Diagnostic; D014316:Tritium