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.

Indomethacin activity in the fetal vasculature of normal and meconium exposed human placentae.

OBJECTIVE: To study the effect of indomethacin on the vasculature of isolated perfused human placental cotyledon in normal and meconium pretreated placentae. STUDY DESIGN: Isolated placental cotyledons were dually perfused and fetal perfusion pressure was used as an index of vascular resistance. Meconium-stained amniotic fluid (MSAF) was collected from patients after artificial rupture of membranes, diluted 1:2, 1:4, 1:16 and 1:32 and a spectrophotometric determination of meconium concentration in amniotic fluid was performed. Only MSAF with an optical density of 20.0 units per gram was used in this study. In five placentae, the effect of indomethacin (100 microg/ml continuous perfusion from the fetal site) on basal pressure of the fetal-placental vasculature was established. In five more placentae, the effect of indomethacin on MSAF-induced vasoconstriction was established when a bolus injections of 1 ml MSAF was made into the fetal circulation. The statistical significance of response to MSAF injection was determined by paired t-test and ANOVA repeated measurements. RESULTS: A significant vasoconstrictor response to MSAF was achieved in normal placentae. Bolus injections of MSAF into the fetal circulation resulted in a significant increase in perfusion pressure (P=0.0026). Indomethacin was capable of significantly reducing the basal perfusion pressure (P=0.03). Significant attenuation of vasoconstrictor response to MSAF occurred in the presence of indomethacin (P=0.0016). CONCLUSION: Indomethacin causes a significant reduction in basal pressure of fetal placental vasculature in the human placental circulation in vitro and is capable of attenuating the vasoconstrictory activity of MSAF. The mechanism of such activity may be explained partially by the inhibitory effect of indomethacin on the PG-mediated pathways.

Increased production of tumor necrosis factor-alpha TNF-alpha by IUGR human placentae.

OBJECTIVE: To evaluate the effect of pathological placental conditions such as intrauterine growth restriction (IUGR) or exposure to angiotensin II (AII) on TNF-alpha secretion in the vasculature of isolated human placental cotyledons. STUDY DESIGN: Isolated placental cotyledons from 10 normal and four intrauterine growth restricted fetuses were dually perfused. Perfusate samples from the fetal circulation were collected every 30 min during 120 min. TNF-alpha levels in the fetal-placental perfusate were evaluated using specific commercial ELISA kits. In three additional normal placentae, bolus injections of angiotensin II (10(-9)-10(-4) mol/l) were given into the fetal-placental circulation and perfusate samples were collected. Statistical significance of difference TNF-alpha levels between different conditions was determined by analysis of variance (ANOVA) and paired t-test. RESULTS: TNF-alpha levels were significantly higher in the perfusate of IUGR placentae as compared with normal placentae after 120 min of perfusion (mean 410+/-121 vs. 39+/-14 pg/ml, P=0.005). There was a significant dose-dependent increase in TNF-alpha levels in the placental perfusate after a bolus injection of AII 66 pg/ml with AII 10(-9) mol/l vs. 97 pg/ml with AII 10(-5) mol/l (P=0.004), respectively. CONCLUSIONS: Placental pathology related to condition IUGR might induce the secretion of proinflammatory cytokines such as TNF-alpha, which may enhance the vasoconstriction of the fetal placental vascular bed.