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Department of Anesthesiology, Tokushima University School of Medicine, Tokushima, Japan
Address correspondence and reprint requests to Dr. Yoshinobu Tomiyama, Department of Anesthesiology, Tokushima University School of Medicine, 3-18-15 Kuramoto, Tokushima 770-8503, Japan. Address e-mail to tomi{at}clin.med.tokushima-u.ac.jp.
The membrane potential of endothelial cells is an important determinant of endothelial functions, including regulation of vascular tone. We investigated whether adenosine triphosphate-sensitive potassium (KATP) channels were involved in the response of membrane potential to hyperosmolality in cultured human aorta endothelial cells. The voltage-sensitive fluorescent dye, bis-(1,3-diethylthiobarbiturate)trimethine oxonol, was used to assess relative changes in membrane potential semiquantitatively. To investigate the effect of mannitol-, sucrose-, and NaCl-induced hyperosmolality on membrane potential, cells were continuously perfused with Earles balanced salt solution (285 mOsm/kg H2O) containing 200 nM bis-(1,3-diethylthiobarbiturate)trimethine oxonol and exposed to 315 and 345 mOsm/kg H2O hyperosmotic medium sequentially in the presence and absence of 1 µM glibenclamide, a well-known KATP channel blocker. Hyperosmotic mannitol significantly induced hyperpolarization of the endothelial cells, which was prevented by 1 µM glibenclamide (n = 6). Estimated changes of membrane potential at 315 and 345 mOsm/kg H2O were 13 ± 8 and 21 ± 8 mV, respectively. Hypertonic sucrose induced similar changes. However, although hypertonic saline also significantly induced hyperpolarization of the endothelial cells (n = 6), the hyperpolarization was not prevented by 1 µM glibenclamide. In conclusion, KATP channels may participate in hyperosmotic mannitol- and sucrose-induced hyperpolarization, but not in hypertonic saline-induced hyperpolarization in cultured human aorta endothelial cells.
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