Development of a sensitive radioimmunoassay for fab fragments : application to fab pharmacokinetics in humans

Anti-sheep Fab fragment antisera were produced in rabbits using sheep digoxin-specific Fab fragments (Digidot) as immunogen. These antisera were used for the development of a radioimmunoassay (RIA) of sheep Fab fragments in human plasma and urine using 125I-labeled Fab fragments. Interference in the...

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Bibliographic Details
Published in:Pharmaceutical research 1993-05, Vol.10 (5), p.692-696
Main Authors: VO THANH-BARTHET, C, URTIZBEREA, M, SABOURAUD, A. E, CANO, N. J, SCHERRMANN, J.-M. G
Format: Article
Language:English
Subjects:
Analysis
Animals
Biological and medical sciences
Digitoxin - poisoning
Digoxin - immunology
Electrophoresis, Polyacrylamide Gel
Enzyme-Linked Immunosorbent Assay
Female
General pharmacology
Half-Life
Humans
Immune Sera - immunology
Immunoglobulin Fab Fragments - blood
Immunoglobulin Fab Fragments - urine
Medical sciences
Middle Aged
Pharmacology. Drug treatments
Radioimmunoassay
Sensitivity and Specificity
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Summary:Anti-sheep Fab fragment antisera were produced in rabbits using sheep digoxin-specific Fab fragments (Digidot) as immunogen. These antisera were used for the development of a radioimmunoassay (RIA) of sheep Fab fragments in human plasma and urine using 125I-labeled Fab fragments. Interference in the assays by digoxin, human proteins, and antibodies from different species was insignificant, but cross-reactivity between anti-sheep Fab antisera and goat IgG or Fab fragments was 22 to 67%. The limit of detection was 0.1 microgram/mL and the assay was linear over a 0.6-28 micrograms/mL range of Fab fragments. Intra- and interassay coefficients of variation were less than 6.9 and 10.5%, respectively. Accuracy of plasma and urine assays at various Fab fragment levels ranged from 96 to 106%. RIA was applied to the pharmacokinetic study of sheep digoxin-specific Fab fragments in one patient acutely intoxicated by digitoxin and treated with Digidot. The Fab elimination half-life was 12.1 hr. Steady-state volume of distribution and total-body clearance were 10.8 L and 23.4 mL/min, respectively. Unchanged Fab fragments (50 kD) and degradation products (25 kD) isolated by gel filtration chromatography of a urine sample cross-reacted with the anti-Fab antiserum.
ISSN:0724-8741
1573-904X
DOI:10.1023/A:1018903614997