Digoxigenin-3,12-dibromoacetate (DDB), an alkylating derivative of digoxigenin, was synthesized and tested as a cardiotonic steroid (CS) site directed affinity label for Na++K+-ATPase (ATP phosphohydrolase EC 126.96.36.199). DDB inhibited rat brain Na++K+-ATPase with an I50 of 5 × 10-6 M and readily displaced specifically bound 3H-ouabain from its binding sites on Na++K+-ATPase. If the enzyme was exposed to DDB prior to the addition of 3H-ouabain its ability to bind 3H-ouabain was decreased, consistent with the concept that DDB interacted irreversibly with the cardiotonic steroid binding sites of Na++K+-ATPase. However, DDB proved to be an even more effective inhibitor of 3H-ouabain binding under conditions where it was unlikely that it could interact with the CS binding sites of this enzyme, suggesting that DDB inhibited 3H-ouabain binding by non-cardiotonic site directed actions. Similarly, the presence of excess strophanthidin did not protect this enzyme against irreversible inhibition by DDB. The data suggest that the presence of a bromoacetate group at the 12 position on cardiotonic steroids does not confer CS binding site directed alkylating properties on these drugs.
|Number of pages||8|
|Journal||European Journal of Pharmacology|
|State||Published - 1975|
Bibliographical noteFunding Information:
This work was supportedb y grantsf rom the Michigan Heart AssociationG, rant HL 16055-01f romthe National Instituteso f Health, and GeneralR esearch Support Grant NIH RR 05623-04t o the Collegeo f VeterinaryM edicine,M ichiganS tateU niversityf,r om the NationalI nstituteso f Health. The authorsw ould like to thank Mrs. Annie Han and Mrs. Marilyn Turn-bow for excellentte chnicaal ssistance.
- Alkylating derivatives
- Cardiotonic steroids
- H-ouabain binding
ASJC Scopus subject areas