MDR1 P-glycoprotein (Pgp), the product of the MDR1 gene involved in multidrug resistance
in cancer cells, is also expressed in normal tissues. In the human kidney, it is localized in the
mesangium, the proximal tubule, the thick ascending limb of Henle's loop, and the collecting
duct. Pgp actively transports lipophilic xenobiotics, peptides, steroids, and lipids, and
perhaps endogenous substrates. It has been shown previously that human mesangial cells
in culture express active Pgp and that the expression of Pgp can be down-regulated by …