Affinity and dose-dependent digoxin Na+K+ATPase dissociation by monoclonal digoxin-specific antibodies.
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.
Cano
N J
NJ
Institut National de la Santé et de la Recherche Médicale, Inserm U26 (Dr. J. M. Bourre), Fernand Widal Hôpital, Paris, France.
Navarro-Teulon
I
I
Debray
M
M
Piechaczyk
M
M
Scherrmann
J M
JM
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000493:pharmacokinetics*; D000915:Antibody Affinity; D000918:Antibody Specificity; D001921:Brain / Q000201:enzymology; D004077:Digoxin / Q000276:immunology / Q000378:metabolism / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D007140:Immunoglobulin Fab Fragments; D008861:Microsomes / Q000201:enzymology; D008962:Models, Theoretical; D011485:Protein Binding; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; C050199:digoxin antibodies Fab fragments; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase