Table 1.

ABC and SLC transporters known to show expression in the human placenta.

Transporter	Syncytiotrophoblast localization	Substrates/function	References
ABCA1	Apical	Cholesterol, phospholipids	[99–101]
ABCB1	Apical	Drug resistance (antibiotics, antiemetic, cardiac drugs, HIV protease inhibitors)	[15, 16, 28]
ABCB4	Basolateral	Bile acids	[24, 38]
ABCC1	Apical	Folate	[28, 32]
ABCC2	Apical	Folate, bilirubin, role in chemoprotection and detoxification	[32, 34, 102, 103]
ABCC3	Apical	Bilirubin	[102]
ABCC4	Apical	Conjugated bile acids	[102]
ABCC5	Basolateral	Cyclic nucleotides	[35]
ABCC7	Apical	Chloride transport	[104]
ABCG1	Basolateral	Cholesterol, phospholipids	[100]
ABCG2	Apical	Drug resistance	[14, 105]
SLCO2A1	Unknown	Prostaglandin	[48]
SLCO2B1	Basolateral	Sulfated steroids (DHEAS), glutamate	[49, 50]
SLCO4A1	Apical	Thyroid hormones	[51]
SLCO1A2	Apical	Thyroid hormones, bile acids, conjugated steroid hormones	[46, 47]
SLCO1B1	Apical	Bile acids	[24]
SLCO3A1	Apical	Bile acids	[24]
SLC22A6	Unknown	Drug xenobiotic eliminator	[56]
SLC22A11	Basolateral	Sulfated steroids (DHEAS)	[57, 58]
SLC22A3	Basolateral	Cationic compounds	[52]
SLC22A5	Apical	Lactate, folate, carnitine	[53–55]
SLC22A4	Apical	Lactate, folate	[59]