title: The placental transfer of acetylsalicylic acid in near-term ewes.
abstract: The placental transfer of acetylsalicylic acid was studied in five near-term ewes and fetuses. The total clearance (Ctot) of acetylsalicylic acid from the fetal compartment was determined by bolus injection of 14C-acetylsalicylic acid into the fetal compartment. Ctot = Cp + Cf where Cp is the placental clearance and Cf is the fetal tissue clearance. 14C-acetylsalicylic acid was then infused into the ewe. Fetal (F) and maternal (M) steady-state concentrations of acetylsalicylic acid were measured. During steady-state conditions, the influx of acetylsalicylic acid into the fetal compartment will equal the efflux, or Cp X (M - F) = Cf X F. Combining these two equations yields the following description of placental clearance: Cp = Ctot x F/M. Using this equation, we calculated Cp = 0.57 +/- 0.12 ml/min . kg and Cf = 1.93 +/- 0.22 ml/min . kg. Maternal and fetal placental flows were also measured using radioactively labeled microspheres. From these flows, a 99% degree of diffusion limitation was determined for the placental transfer of acetylsalicylic acid.
mesh_terms: D000818:Animals; D001241:Aspirin / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002855:Chromatography, Thin Layer; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D008657:Metabolic Clearance Rate; D010920:Placenta / Q000098:blood supply / Q000378:metabolism; D011247:Pregnancy; D011485:Protein Binding; D012306:Risk; D012756:Sheep; D014462:Ultrafiltration
chemical_list: D002250:Carbon Radioisotopes; D001241:Aspirin