P-glycoprotein expression of the human placenta during pregnancy

Objective: To investigate whether the placental expression of P-glycoprotein shows a quantitative difference during pregnancy. Study design: Villous tissue was collected from chorionic villus samples (13-14 weeks of gestation; n = 33 and 20-25 weeks of gestation; n = 4) and from full-term placentas (38-41 weeks of gestation; n = 28). P-glycoprotein was detected by western blot analysis and quantified by densitometry. Results: We showed for the first time a significant and progressive two-fold decrease in the mean expression of P-glycoprotem between early and late samples, with a major overlap of values. Conclusion: As P-glycoprotein appears to be involved in drug extrusion, these data suggest that the placenta's ability to protect the fetus from xenobiotics is greater in early pregnancy than at term.