Characterization of organic anion transporters in cultured rat and human osteoblast cells

Abstract

The excretion of organic anions is mainly performed by transport protein in the kidney and liver. Several integral membrane protein families serve as organic anion transporters. There are ATP binding cassette, organic anion transporting protein and organic anion transporter (OAT). Among these OATs (including OAT1, 2 and 3) have extremely wide spectrum of substrate specificity. They mainly expressed in the brain, liver and kidney. The purpose of this study is to clarify the expression and characterization of OATs in cultured rat and human osteoblast cells. The expression of OAT1, 2 and 3 was determined using reverse transcription‐polymerase chain reaction (PCR) and Western blotting analysis. Among these three isoforms of OATs, OAT3 messenger RNA was detected in cultured rat osteoblast cells. No RT‐PCR products of OAT2 and 3 were observed. By Western blot analysis, OAT3 protein was detected in plasma membrane fraction. The isotope labeled para‐aminohippuric acid, estrone sulfate and dehydroepiandrosterone sulfate uptake at 37¡ÆC were significantly increased comparing those of control (at 0–4¡ÆC). The uptake was inhibited by some organic anion chemical/drug and several sulfate conjugates. From these results, obtained data would contribute to understanding of therapeutics and pathophysiology of bone disease.