Objectives: T-2307, a novel arylamidine synthesized at Toyama Chemical Co., Ltd, has in vitro and in vivo broad-spectrum activities against pathogenic fungi. T-2307 particularly exhibits potent in vitro and in vivo activity against Candida albicans, suggesting that its uptake might be mediated by a transport system. In this report, we studied the uptake of T-2307 in C. albicans.
Methods: C. albicans cells and rat hepatocytes were exposed to 0.02 microM [(14)C]T-2307. After incubation, the reaction mixture was concentrated and layered on a silicon layer (mixture of silicon oil and liquid paraffin) inside a tube. The tube was then centrifuged to transfer cells into the bottom layer (sodium hydroxide) for solubilization. The bottom layer was neutralized and measured for radioactivity.
Results: T-2307 was concentrated from the extracellular medium by C. albicans cells in 10 mM phosphate buffer solution supplemented with 1% glucose by 3200- to 5100-fold. The accumulation was approximately two orders of magnitude greater than that achieved with a rat hepatocyte preparation. T-2307 uptake was sensitive to temperature and extracellular pH, and was reduced in the presence of inhibitors of mitochondrial respiration, oxidative phosphorylation and plasma membrane proton pump, and by an uncoupler. Furthermore, T-2307 uptake was concentration dependent and an Eadie-Hofstee plot suggested the involvement of two transport systems.
Conclusions: The considerably higher concentrations of T-2307 were selectively accumulated in C. albicans via transporter-mediated systems, as compared with the concentrations in rat hepatocytes. This transporter-mediated uptake of T-2307 contributes to its potent anticandidal activity.