title: Radioreceptor assay for quantifying FK-506 immunosuppressant in whole blood.
abstract: We describe a quantitative radioreceptor assay (RRA) for quantifying FK-506 in whole blood. FK-506 extracted from whole blood with a cyclohexyl-sorbent column competes with [3H]dihydro-FK-506 for binding to a partially purified preparation of FK-506 binding protein (FK-BP). Free and protein-bound FK-506 are separated on LH 20 Sephadex chromatographic columns. We compared the results of this method with those of an enzyme immunoassay that uses a monoclonal antibody: r = 0.97, Sy/x = 0.039. Between-day precisions (CV) at FK-506 concentrations of 8 and 17 micrograms/L were 9.2% and 8.2%, respectively. Within-run precisions were 5.9%, 8.1%, and 9.4%, respectively, at 4, 8, and 15 micrograms/L. Analytical recovery, evaluated at 5, 10, 15, 20, and 25 micrograms/L for FK-506 added to whole blood, ranged from 98% to 103%. The assay can reliably quantify FK-506 blood concentrations between 1.0 and 25 micrograms/L.
authors.affiliation: Department of Laboratory Medicine, Children's National Medical Center, Washington, DC 20010.
authors.forename: J N
authors.initials: JN
authors.lastname: Murthy
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: V S
authors.initials: VS
authors.lastname: Warty
authors.forename: R
authors.initials: R
authors.lastname: Venkataramanan
authors.forename: J G
authors.initials: JG
authors.lastname: Donnelly
authors.forename: A
authors.initials: A
authors.lastname: Zeevi
authors.forename: S J
authors.initials: SJ
authors.lastname: Soldin
mesh_terms: D002851:Chromatography, High Pressure Liquid; D016027:Heart Transplantation; D006801:Humans; D007124:Immunoenzyme Techniques; D011786:Quality Control; D011869:Radioligand Assay / Q000379:methods* / Q000706:statistics & numerical data; D016559:Tacrolimus / Q000097:blood*
chemical_list: D016559:Tacrolimus