Xenobiotic transporter gene expression in isolated lactating and non-lactating human mammary epithelial cells

Despite the documented benefits of breastfeeding and major governmental advocacy efforts, a paucity of data exists regarding the transfer of most drugs into breast milk. Passive diffusion governs the extent of accumulation for most drugs and the exposure risk can therefore be predicted using mathematical models. However, examples of xenobiotic accumulation into breast milk well above that predicted by passive diffusion have been documented and attributed to drug transport. A thorough evaluation of the expression of xenobiotic transporters in mammary epithelial cells (MECs), the cells that form the anatomical barrier between maternal serum and breastmilk, during lactation is necessary to determine the drugs for which an active transport mechanism governs transfer into breast milk and to improve predictive models.

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