[Cardiac glycosides and metabolites--problems of recovery in tissue extracts. Separation of visible substance spots in the nanogram range (author's transl)].

The recovery measurements in rat tissues performed via i.p. injected radioactive digoxin derivates (3H-digoxin, 125J-digoxin derivative) showed that approximately 50% of the total glycoside content will be extracted. Thus, an addition of digoxin standards to drug-free tissues may lead to false negative determinations. By comparison of the radioactivity before and after extraction the following results were obtained: Recovery from tissues 3H-digoxin 50% 125J-digoxin 40% from serum 3H-digoxin 60% added to drug free tissue homogenates 3H-digoxin 85% After i.p. application of 15 mg/kg of beta-methyldigoxin to BD9 (Berlin)-rats the resulting tissue concentrations were extracted by Amberlite XAD-2. beta-Methyldigoxin and its metabolites digoxin and digoxinbisdigitoxide could be separated and distinguished from artifacts by fluorescence detection on HPTLC-plates with a detection limit of 60 ng/spot. Concentration determined by radioimmunoassay are in satisfactory agreement with HPTLC results.