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Swelling-Activated Anion Channels Are Essential for Volume Regulation of Mouse Thymocytes
Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Acad. Sci. RUz, Tashkent 100095, Niyazova 1, Uzbekistan
Department of Biophysics, National University, Tashkent 100174, Vuzgorodok, Uzbekistan
* Author to whom correspondence should be addressed.
Received: 25 October 2011; in revised form: 10 November 2011 / Accepted: 24 November 2011 / Published: 8 December 2011
Abstract: Channel-mediated trans-membrane chloride movement is a key process in the active cell volume regulation under osmotic stress in most cells. However, thymocytes were hypothesized to regulate their volume by activating a coupled K-Cl cotransport mechanism. Under the patch-clamp, we found that osmotic swelling activates two types of macroscopic anion conductance with different voltage-dependence and pharmacology. At the single-channel level, we identified two types of events: one corresponded to the maxi-anion channel, and the other one had characteristics of the volume-sensitive outwardly rectifying (VSOR) chloride channel of intermediate conductance. A VSOR inhibitor, phloretin, significantly suppressed both macroscopic VSOR-type conductance and single-channel activity of intermediate amplitude. The maxi-anion channel activity was largely suppressed by Gd3+ ions but not by phloretin. Surprisingly, [(dihydroindenyl)oxy] alkanoic acid (DIOA), a known antagonist of K-Cl cotransporter, was found to significantly suppress the activity of the VSOR-type single-channel events with no effect on the maxi-anion channels at 10 μM. The regulatory volume decrease (RVD) phase of cellular response to hypotonicity was mildly suppressed by Gd3+ ions and was completely abolished by phloretin suggesting a major impact of the VSOR chloride channel and modulatory role of the maxi-anion channel. The inhibitory effect of DIOA was also strong, and, most likely, it occurred via blocking the VSOR Cl− channels.
Keywords: thymocytes; volume regulation; anion channels; phloretin; DIOA
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Kurbannazarova, R.S.; Bessonova, S.V.; Okada, Y.; Sabirov, R.Z. Swelling-Activated Anion Channels Are Essential for Volume Regulation of Mouse Thymocytes. Int. J. Mol. Sci. 2011, 12, 9125-9137.
Kurbannazarova RS, Bessonova SV, Okada Y, Sabirov RZ. Swelling-Activated Anion Channels Are Essential for Volume Regulation of Mouse Thymocytes. International Journal of Molecular Sciences. 2011; 12(12):9125-9137.
Kurbannazarova, Ranokhon S.; Bessonova, Svetlana V.; Okada, Yasunobu; Sabirov, Ravshan Z. 2011. "Swelling-Activated Anion Channels Are Essential for Volume Regulation of Mouse Thymocytes." Int. J. Mol. Sci. 12, no. 12: 9125-9137.