1. ¹Department of Cell Physiology, National Institute for Physiological Sciences, Myodaiji-cho, Okazaki 444-8585, Japan
2. ²Department of Anesthesiology, The First Affiliated Hospital, China Medical University, Shenyang 110001, China
3. ³Japan Society for the Promotion of Science (JSPS), Okazaki 444-8585, Japan
4. ⁴Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
5. ⁵Department of Biophysics, National University, Tashkent 700174, Vuzgorodok, Uzbekistan

Correspondence: Yasunobu Okada, Tel: +81-564-55-7731; Fax: +81-564-55-7735 E-mail: okada@nips.ac.jp

^*These two authors contributed equally to this work.

Received 20 May 2007; Revised 20 August 2007; Accepted 7 November 2007.

Abstract

In the present study, we aimed to evaluate the pathways contributing to ATP release from mouse astrocytes during hypoosmotic stress. We first examined the expression of mRNAs for proteins constituting possible ATP-releasing pathways that have been suggested over the past several years. In RT-PCR analysis using both control and osmotically swollen astrocytes, amplification of cDNA fragments of expected size was seen for connexins (Cx32, Cx37, Cx43), pannexin 1 (Px1), the P2X7 receptor, MRP1 and MDR1, but not CFTR. Inhibitors of exocytotic vesicular release, gap junction hemi-channels, CFTR, MRP1, MDR1, the P2X7 receptor, and volume-sensitive outwardly rectifying chloride channels had no significant effects on the massive ATP release from astrocytes. In contrast, the hypotonicity-induced ATP release from astrocytes was most effectively inhibited by gadolinium (50 M), an inhibitor of the maxi-anion channel, which has recently been shown to serve as a pathway for ATP release from several other cell types. Thus, we propose that the maxi-anion channel constitutes a major pathway for swelling-induced ATP release from cultured mouse astrocytes as well.