Table 1.

Tissues in which P-gp is expressed and has physiological efflux roles.

Tissue	P-gp expression sites	References
Adrenal gland	Glandular cells in medulla and cortex	[17]
Basal ganglia	Glial cells	[18]
Cerebral cortex	Blood luminal membrane of the brain capillary endothelial cells	[11]
	End-feet of astrocytes
Colon	Apical surface of columnar epithelial cells	[17]
Fallopian tubes	Apical portion of epithelial cells	[19]
Gallbladder	Glandular cells	[18]
Hippocampus	Microglia	[20]
Kidney	Renal proximal tubular cells	[21, 22]
Liver	Cholangiocytes	[17, 18]
	Biliary canalicular surface of hepatocytes
Ovaries	Follicle cells, oocytes, somatic cells of the ovary	[19, 23]
Pancreas	Apical surface of small ductules	[17]
Placenta	Apical microvilli membrane of syncytiotrophoblast	[21, 24]
Small intestine	Glandular cells	[17, 21]
	Apical membranes of epithelial cells
Testicles	Endothelial capillary cells	[22]
	Leydig cells
	Early spermatids