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OAT - Organic Anion Transporters

The organic anion transporters (OATs) belong to the solute carrier family (SLC) 22A with 12 transmembrane domains and are mainly expressed in the apical or basolateral membrane of the renal proximal tubules, the site of active drug secretion. However, OATs are also expressed in the liver and also with a lower expression in other organs like brain, placenta and testis.

OAT2 is identified to be expressed in the basolateral membrane of proximal tubules and in the sinusoidal membrane of hepatocytes, while OAT3 is primarily expressed in the kidney and play critical role in renal drug transport. Sex differences are known for the expression of human OAT2. In experimental animals like rats and mouse, chemotherapy agents like cisplatin or methotrexate lead to a decrease of Oat1 and Oat3 abundance, while other drugs like the loop diuretic furosemide increase the expression of Oat3.
In contrast to other transporters of the SLC22A family, OATs have the ability to exchange extracellular against intracellular organic anions. Typical probe substrates are e.g. aminohippurate (PAH) for OAT1and estrone-3-sulfate (ES) for most other OATs, but for many drugs like ACE inhibitors (e.g. captopril), angiotensin II receptor blockers (e.g. losartan, valsartan) or antineoplastic drugs (e.g. methotrexate) and uricosuric drugs (e.g. benzbromarone) a OAT mediated transport have been shown. For a full review see Burckhardt, 2012: Pharmacol Ther. 2012 Oct;136(1):106-30. doi: 10.1016/j.pharmthera.2012.07.010. Epub 2012 Jul 25

In cooperation with the University Medicine of Greifswald, Department of Clinical Pharmacology, Primacyt is offering stable transfected HEK293 cells expressing human OATs. All cells are validated for expression rates, localization of the overexpressed transporter protein and functionality. We analyze the uptake functions using suitable substrates, inhibiting the uptake by adding the reference inhibitors.