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OAT1 (SLC22A6)

Molecular structure and Tissue distribution
OAT1 was the first organic anion transporter to be cloned from several species. The gene for hOAT1, SLC22A6, is located on chromosome 11q12.3., being paired with the gene for hOAT3 (SLC22A8). The secondary structure analysis of the hOAT1 protein predicted 12 transmembrane helices with the N- and C-termini located at the cytosolic side of the plasma membrane. Immunohistological studies revealed the expression of OAT1 at the basolateral membrane of proximal tubule cells in human kidneys and brain.

Interaction of OAT1 with endogenous compounds and drugs
OAT1 interacts with a huge number of endogenous organic anions. OAT1 mediate transport of many endogenous organic anions (a-ketoglutarate, prostaglandin E2, prostaglandin F2a, cAMP, cGMP, folate, and urate) has been demonstrated by several research groups. Numerous other endogenous compounds inhibit OAT1 function, e.g. corticosterone, dehydroepiandrosterone sulfate, estrone sulfate, nicotinate, xanthine, hypoxanthine and several acidic metabolites of neurotransmitters  norepinephrine and dopamine, such as vanillinemandelate and 3,4-dihydroxyphenylacetate, homovanillate, respectively. Several studies have demonstrated the interaction of OAT1 with exogenous compounds like antibiotics, diuretics, NSAID (non-steroidal anti-inflammatory drugs), anivirals, cytostatics and toxins. OATs mediated transport has been shown for some of these substances, including tetracycline, acyclovir, adefovir, bumetanide, furosemide, ibuprofen, indomethacin, methotrexate and ochratoxin A. A vast number of drugs such as antibiotics (benzylpenicillin, cephaloridine), diuretics (torasemide, chlorothiazide), NSAID (acetylsalicylate, diclofenac), antihpertensives (captopril, losartan), cytostatics  (chlorambucil), statins (pravastatin, fluvastatin) and uricosurics (probenecid, benzbromaron) inhibit OAT1 activity. The direct OAT1 mediated translocation of these drugs has not been examined yet.

Figure 1 Concentration dependent OAT1 mediated PAH uptake Figure 2 Inhibition of OAT1 mediated PAH uptake by glibenclamide




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