title: Transport of [3H]losartan across isolated perfused rabbit proximal tubule.
abstract: The transport of the angiotensin II receptor antagonist losartan and its interaction with organic anion transport were examined in the isolated perfused rabbit proximal tubule. Losartan reversibly inhibited the secretion of para-aminohippurate (PAH) in a concentration-dependent manner (IC50 = 15 +/- 0.5 microM). Other angiotensin II receptor antagonists also inhibited PAH secretion with similar potencies: eprosartan, 11 +/- 2.3 microM; irbesartan, 17 +/- 2.2 microM; and valsartan 3 +/- 0.6 microM. [3H]Losartan was secreted by the proximal tubule by a saturable and probenecid-sensitive mechanism. The affinity of losartan for the organic anion transporter (Km = 12.3 +/-1.8 microM) was significantly greater than that of PAH (Km = 88.5 +/- 10.7 microM). [3H]Losartan secretion was stimulated in the presence of alpha-ketoglutarate, suggesting that losartan, like PAH, enters the cell in exchange for a dicarboxylate. These results demonstrate that losartan and probably other nonpeptide angiotensin II receptor antagonists are secreted by an organic anion transporter that is similar to, if not identical with, the classic PAH transporter.
authors.affiliation: Department of Renal Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania, USA. Richard_M_Edwards@sbphrd.com
authors.forename: R M
authors.initials: RM
authors.lastname: Edwards
authors.forename: E J
authors.initials: EJ
authors.lastname: Stack
authors.forename: W
authors.initials: W
authors.lastname: Trizna
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D066298:In Vitro Techniques; D007656:Ketoglutaric Acids / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D019808:Losartan / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D011339:Probenecid / Q000494:pharmacology; D011817:Rabbits; D012076:Renal Agents / Q000494:pharmacology; D010130:p-Aminohippuric Acid / Q000378:metabolism / Q000494:pharmacology
chemical_list: D057911:Angiotensin Receptor Antagonists; D007656:Ketoglutaric Acids; D012076:Renal Agents; D000804:Angiotensin II; D019808:Losartan; D011339:Probenecid; D010130:p-Aminohippuric Acid