Na+-dependent carnitine transport by organic cation transporter (OCTN2): Its pharmacological and toxicological relevance

Rikiya Ohashi, Ikumi Tamai, Hikaru Yabuuchi, Jun Ichi Nezu, Asuka Oku, Yoshimichi Sai, Miyuki Shimane, Akira Tsuji

研究成果: ジャーナルへの寄稿学術論文査読

243 被引用数 (Scopus)

抄録

Carnitine deficiency, either primary or drug-induced, causes critical symptoms and is thought to involve alteration of active transport of carnitine across the plasma membrane of tissues as the underlying mechanism. Recently, we showed that human organic cation transporter, hOCTN2, cloned as a member of the organic cation transporter family, is a physiologically important Na+-dependent high-affinity carnitine transporter in humans. In this study, we further characterized the functional properties of hOCTN2 and examined the interaction between hOCTN2-mediated carnitine transport and clinically used drugs to assess possible toxicological effects. When expressed in human embryonic kidney (HEK)293 cells, hOCTN2 showed low but significant stereospecific transport activity: D-carnitine was transported with lower affinity (K(m) = 10.9 μM) than the L-isomer (K(m) = 4.3 μM). One Na+ appeared to be associated with the transport of one carnitine molecule, hOCTN2-mediated transport of acetyl-L-carnitine was also Na+-dependent and of high affinity, with a K(m) value of 8.5 μM. To examine the transport activity for organic cations other than carnitine and the possible relationship of drug-induced carnitine deficiency with hOCTN2, the inhibitory effect of several drugs on hOCTN2-mediated L-carnitine transport was examined. Many zwitterionic drugs, such as cephaloridine, and many cationic drugs, such as quinidine and verapamil, exhibited significant inhibitory effects. Among these inhibitors, tetraethylammonium, pyrilamine, quinidine, verapamil, and valproate were found to be transported by hOCTN2. The results suggest that the carnitine deficiency-related toxicological effects by long- term treatment with such drugs might be ascribed to a functional alteration of hOCTN2-mediated carnitine transport.

本文言語英語
ページ(範囲)778-784
ページ数7
ジャーナルJournal of Pharmacology and Experimental Therapeutics
291
2
出版ステータス出版済み - 11-1999

All Science Journal Classification (ASJC) codes

  • 分子医療
  • 薬理学

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