title: Modification of vulnerability to dodecylbenzenesulfonate, an anionic surfactant, by calcium in rat thymocytes.
abstract: We have previously reported that cremophor EL, a nonionic surfactant, at clinical concentrations significantly decreases the cell viability of rat thymocytes with phosphatidylserine-exposed (PS-exposed) membranes under in vitro condition. It is reminiscent of a possibility that sodium dodecylbenzenesulfonate (DCBS), an anionic surfactant world-widely used for detergents, also affects the cells in the similar manner. To test the possibility, the effect of DCBS on rat thymocytes has been examined using a flow cytometer with fluorescent probes. Exposure of PS on outer surface of cell membranes was induced by A23187, a calcium ionophore to increase intracellular Ca(2+) concentration ([Ca(2+)](i)). DCBS at 1μg/mL (2.87μM) significantly decreased the viability of cells with PS-exposed membranes, but not with intact membranes. DCBS also significantly decreased the viability of cells exposed to H(2)O(2), an oxidative stress increasing the [Ca(2+)](i). On the other hand, the decrease in extracellular Ca(2+) concentration ([Ca(2+)](e)) increased the cell vulnerability to DCBS and vice versa. Intact membrane lipid bilayer and extracellular Ca(2+) are required to maintain membrane integrity. Therefore, the change of membrane property by manipulation of [Ca(2+)](i) and [Ca(2+)](e) is one of causes for the augmentation of DCBS cytotoxicity.
authors.affiliation: Laboratories of Cell Signaling and Environmental Chemistry, Faculty of Integrated Arts and Sciences, The University of Tokushima, Tokushima 770-8502, Japan.
authors.forename: Jun-Ya
authors.initials: JY
authors.lastname: Yamaguchi
authors.forename: Aimi
authors.initials: A
authors.lastname: Kanada
authors.forename: Kanna
authors.initials: K
authors.lastname: Horimoto
authors.forename: Tomohiro M
authors.initials: TM
authors.lastname: Oyama
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Chikutei
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Shiro
authors.initials: S
authors.lastname: Ishida
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Okano
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Oyama