DIGOXIN TRANSFER ACROSS THE ISOLATED PLACENTA IS INFLUENCED BY MATERNAL AND FETAL ALBUMIN CONCENTRATIONS

The aim of this study was to evaluate the influence of different mater nal and fetal albumin concentrations on the transplacental transfer an d the placental tissue accumulation of digoxin. Digoxin passage across the isolated lobules of 15 human placentae was calculated from repeat ed fetal and maternal perfusate samples, and placental tissue digoxin concentrations were measured at the end of the experiments. Metildigox in (Lanitop) was added to the maternal medium at a concentration of 5. 70 +/- 0.73 ng mL(-1), and maternal and fetal perfusate albumin (BSA) concentrations were kept equal either at a high concentration of 21 g L(-1) (Group I; n = 5) or at a low concentration of 3 g L(-1) (Group I II; n = 5), or differed with a materno-fetal gradient of 21:3 g L(-1) (Group II; n = 5). In the experiments with low maternal albumin concen trations (Group III), digoxin concentrations in the maternal circuit d ecreased to 3.56 ng mL(-1), whereas digoxin concentrations in the feta l circuit reached 2.59 ng mL(-1) over a 3-h period. With maternal BSA concentrations of 21 g L(-1) (Group I and Group II), the decrease in d igoxin concentration in the maternal circuit was lower (P < 0.05), and digoxin tissue concentrations at the end of the experiments were smal ler (0.45 +/- 0.07 and 0.42 +/- 0.03 v. 0.82 +/- 0.32 ng mg(-1) protei n, Group I and Group II v. Group III respectively; P < 0.05). Comparin g only those lobules with similar high concentrations of maternal prot ein, fetal BSA concentrations of 21 g L(-1) resulted in a greater incr ease in digoxin concentrations in the fetal circuit (end-fete to initi al-maternal digoxin concentrations of 0.44 +/- 0.08 v. 0.37 +/- 0.04 n g mg(-1) protein (Group I v. Group If respectively), although this was not significant. The data suggest that maternal and fetal serum album in concentrations may have an influence on transplacental digoxin tran sfer, and this should be considered when treating fetuses with cardiac disease transplacentally with glycosides.