• Takeshi Yamagiwa, Sadaki Inokuchi, Takeshi Saito, Shigeaki Inoue, Seiji Morita, and Akira T Kawaguchi.
• Department of Emergency and Critical Care Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan. yamagiwa@is.icc.u-tokai.ac.jp.
• Tokai J. Exp. Clin. Med. 2013 Jan 1; 38 (4): 114-22.

BackgroundHydrogen cyanide possesses a high acid-dissociation constant of 9.14, favoring its vaporization and depletion from the culture media at physiological pH, which may cause the cyanide toxicity unstable in vitro.ObjectiveWe investigated whether adjustment of culture medium pH stabilizes cyanide concentration and decreases the effective concentration of potassium cyanide (KCN).MethodsMurine fibroblast cells were exposed to different concentrations of KCN in media maintained at pH 7.4 or 9.2, in the presence or absence of hydroxocobalamin. After incubation for 1 h, we evaluated medium pH, cyanide concentration, cytochrome activity, and cell viability.ResultsCyanide concentration decreased to 18.8% in pH 7.4 medium compared to 83.2% in pH 9.2 medium. A significant decrease in cytochrome activity was observed at 40 mM and 1.25 mM KCN in pH 7.4 and pH 9.2 media, respectively. In pH 9.2 medium, dose-dependent cytotoxicity of KCN and antidotal effects of hydroxocobalamin were observed.ConclusionAdjustment of culture medium pH to 9.2 could stabilize cyanide concentration and decrease the effective concentration of KCN, allowing stable evaluation of KCN toxicity and antidotal efficacy.

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