Properties of novel anti-digoxin antisera in radioimmunoassay using homologous and site heterologous tritium-labeled antigens involving a [3H]-leucine moiety.
The specificities of antisera against digoxin C-3' or C-3'' hemisuccinate-bovine serum albumin (BSA) conjugate were assessed by cross-reactivity studies with digoxin metabolites by radioimmunoassay (RIA) using the homologous and the site heterologous tritium-labeled antigens. One of the tracers used was digoxin 3'-hemisuccinyl-[3H]-leucine; the other was digoxin 3''-hemisuccinyl-[3H]-leucine, which had been prepared from digoxin 3''-hemisuccinate. When the tracer with [3H]-leucine at the C-3' position was used, antisera (I-1, I-3) elicited by digoxin 3'-hemisuccinate-BSA conjugate showed the following cross-reactivity: digoxigenin bisdigitoxoside (0.34%, 76%), digoxigenin monodigitoxoside (0.11%, 65%), digoxigenin (0.02%, 26%) and dihydrodigoxin (9.4%, 1.2%). However, when using the homologous antigen, antiserum (I-1) was highly specific against the digitoxose chain. When the site heterologous antigen, digoxin 3''-hemisuccinyl-[3H]-leucine was combined, this antiserum showed high cross-reactivity to digoxin degradation products. This digoxin RIA using antiserum (I-1) with the homologous antigen measures unmetabolized digoxin. On the other hand, the RIA system using antiserum (I-3) with the homologous antigen had cross-reactivity with the metabolites in accordance with their relative cardio-activities, so this system would be useful in therapeutic drug monitoring of digoxin.
Ikeda
Yukari
Y
Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3, Kanagawa-machi, Kanazawa 920-1181, Japan. y-ikeda@hokuriku-u.ac.jp
Fujii
Youichi
Y
D000818:Animals; D015478:Antigens, Heterophile / Q000032:analysis / Q000378:metabolism*; D002417:Cattle; D004077:Digoxin / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007106:Immune Sera / Q000032:analysis / Q000378:metabolism*; D007930:Leucine / Q000032:analysis / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011863:Radioimmunoassay / Q000379:methods; D012710:Serum Albumin, Bovine / Q000032:analysis / Q000378:metabolism*; D014316:Tritium / Q000032:analysis / Q000378:metabolism*
D015478:Antigens, Heterophile; D007106:Immune Sera; C085465:digoxin 3'-hemisuccinate-bovine serum albumin conjugate; D014316:Tritium; D012710:Serum Albumin, Bovine; D004077:Digoxin; D007930:Leucine