In Vitro Transport Mechanism of Psoralen in a Human Placental Cell Line (BeWo Cells)

The mechanism by which psoralen is transported across the placenta was investigated in the BeWo human placental cell line derived from choriocarcinoma in a transwell assay system using liquid chromatography-mass spectrometry/mass spectrometry detection. Psoralen uptake by BeWo cells increased linearly over the concentration range of 0.01 mu M to 100 mu M (r(2) = 0.997) and was not saturable. Psoralen uptake by BeWo cells was not affected by temperature (4 degrees C, room temperature, and 37 degrees C; p > 0.05). Psoralen transport increased linearly over 180 min (r(2) = 0.988) with 3.08 +/- 0.26%, 5.47 +/- 0.21%, 7.54 +/- 0.06%, 9.40 +/- 0.37%, 11.49 +/- 0.31%, and 12.46 +/- 0.61% transferred from the apical chamber to the basolateral chamber in the transwell assays at 30, 60, 90, 120, 150, and 180 min, respectively. The rate of transport showed the same tendency, increasing linearly from 0.13 +/- 0.01 pmol/s to 0.58 +/- 0.03 pmol/s over the concentration range of 25 mu M to 100 mu M (r(2) = 0.989). The apparent permeability coefficient for psoralen (100 mu M) was 5.62 +/- 0.24 x 10(-6) cm/s and 5.53 +/- 0.47 x 10(-6) cm/s before and after treatment with verapamil (100 mu M), respectively (p > 0.05). The efflux value for psoralen was approximately 1. These data show that psoralen is well absorbed and crosses the placental barrier via passive diffusion in the BeWo cell line.