Albumin-dependent digoxin transfer in isolated perfused human placenta

Objective: To determine the effects of albumin (BSA) concentration in perfusion medium on digoxin transfer in isolated perfused human placental cotyledon. Study design: Isolated placental cotyledons from 13 normal human placentas were dually perfused after cannulating artery and vein of the chorionic plate and piercing 4 catheters through the corresponding basal plate with M199 medium enriched with BSA and glucose. Flow rates were 12 and 6 ml/min in the maternal and fetal circuits, respectively. Digoxin was added to the maternal reservoir at a final concentration of 5.51 ± 1.00 ng/ml. BSA in maternal and fetal perfusate was kept at 3 concentrations: 1, 3 and 5 mg/ml (Groups I, II, III). Transplacental passage of digoxin was calculated from repeated fetal and maternal perfusate samples collected over 3 hours in the 3 groups. Digoxin levels were measured by FPIA (TDx, Abbott). Results: There was no transfer of digoxin from the maternal to fetal compartment when the concentration of BSA was 1 mg/ml. Increasing the concentration of BSA led to a substantial increase in the transfer of digoxin to the fetal compartment. Steady state levels of digoxin in the fetal compartment were 0.61 ± 0.19 ng/ml at 3 mg/ml of BSA. Conclusion: Maternal and fetal serum concentration of BSA affect digoxin transfer in isolated perfused human placentas. Three mg/ml are considered to be the optimal albumin concentration.