Analytical Sciences

Arachidonic Acid-Induced Channel- and Carrier-Type Ion Transport across Planar Bilayer Lipid Membranes

Ayumi HIRANO, Yuko NAMATAME, Eiichi WAKAIZUMI, Yuka MATSUNO, and Masao SUGAWARA 

Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajousui, Setagaya, Tokyo 156-8550, Japan

Transmembrane ion transport by arachidonic acid (AA) through bilayer lipid membranes (BLMs) was investigated by means of electrochemical measurements to provide a basis for designing a sensor membrane. We found that AA induces a channel-type current, in addition to a carrier-type current, across planar BLMs. A linear relation between the logarithmic value of the AA concentration and the current responses (given as integrated currents) was observed for a carrier-type current, while a sigmoid relation was found for a channel-type current. Although AA transports Na⁺, Ca²⁺ and Mg²⁺ and exhibits ion selectivity between Na⁺ and Mg²⁺ for the carrier-type current, ion transport for the channel-type current was non-selective. It was found that ion transport via the channel mechanism occurs frequently for AA, while channel-type currents were only occasionally observed for gamma-linolenic acid and prostaglandin D₂. No channel-type currents were induced by other fatty acids (oleic, linoleic, stearic, myristic, eicosapentanoic and docosahexanoic acids) and metabolites of AA (12-HETE and 5-HETE). The carrier-type ion transport occurs selectively to these compounds if the concentration is below 1.0 uM. These results suggest that AA selectively facilitates an ion flux through the BLMs, generating channel-type and/or carrier-type currents, which can be used as a measure of the AA concentration.

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