Affinity and dose-dependent digoxin Na +K +ATPase dissociation by monoclonal digoxin-specific antibodies

• Published in: Biochemical pharmacology Vol. 50; no. 11; pp. 1867 - 1872
• Main Authors: Cano, Nathalie J., Navarro-Teulon, Isabelle, Debray, Marcel, Piechaczyk, Martine, Scherrmann, Jean-Michel
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 27.11.1995; Elsevier Science
• Subjects: affinity; Animals; Antibodies, Monoclonal - immunology; Antibodies, Monoclonal - pharmacokinetics; Antibody Affinity; Antibody Specificity; Biological and medical sciences; Brain - enzymology; digoxin; Digoxin - immunology; Digoxin - metabolism; Digoxin - pharmacokinetics; dissociation kinetics; Dose-Response Relationship, Drug; Drug intoxications. Doping; Immunoglobulin Fab Fragments; Medical sciences; Microsomes - enzymology; Models, Theoretical; monoclonal antibodies, rat brain Na +K +ATPase; Pharmacology. Drug treatments; Protein Binding; Rats; Sodium-Potassium-Exchanging ATPase - metabolism; IgG, immunoglobulin G; EDTA, ethylene diamine tretraacetic acid; monoclonal antibodies, rat brain Na +K +ATPase; AAC, area above the curve; ELISA, enzyme linked immunosorbent assay; Fab, fragment antigen binding; dissociation kinetics; Mab, monoclonal antibody; digoxin; SABS, specific active binding sites; affinity; Ka, affinity constant; Cardiotonic agent; Toxicity; Central nervous system; Monoclonal antibody; K; Microsome; Na; Glycoside; Dissociation; Digitalis drug; Enzyme; Drug intoxication; Rodentia; Detoxication; In vitro; Vertebrata; Biological fixation; Mammalia; Mouse; Animal; Hydrolases; Affinity; exchanging ATPase; Kinetics; Comparative study; Brain (vertebrata)
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/0006-2952(95)02080-2

The effect of three monoclonal digoxin-specific antibodies and of polyclonal Digidot ® as reference on digoxin dissociation from rat brain Na +K +ATPase microsomes was studied to determine the role of the affinity constant (Ka) and dose of the antibody on the rate of digoxin dissociation from Na +K +ATPase. Stoichiometrical doses of 1C10, 6C9, 9F5 IgG, and Digidot ® ( Ka = 6 10 9, 3.1 10 8, 2.5 10 7, and 8.5 10 9 M −1, respectively) resulted in digoxin dissociation related to Ka. When the IgG:digoxin molar ratio increased from 0.25 to 10, digoxin dissociation from Na +K +ATPase sites also increased according to the Hill equation, allowing comparative parameters among the three antibodies to be determined. 1C10 IgG was 2- and 10-fold more efficacious than 6C9 and 9F5, respectively. This in vitro model appears to be a useful predictive screening assay before in vivo experimentation.