Affiliation:
1. University of Pennsylvania School of Medicine, Department of Medicine, Division of Hematology/Oncology, 730 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104-6160, USA
Abstract
The reduction of 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT) and other tetrazolium salts is widely used as an assay for bacterial, fungal and mammalian cell viability, but the genes encoding the reductase activities have not been defined. Here, it was shown that XTT and plasma membrane ferric reductase activities were 10–40-fold greater inCandida albicansthan inSaccharomyces cerevisiae. XTT reductase activity was induced fivefold inC. albicansgrown in low-iron conditions compared with iron-replete conditions, and for cells grown in unbuffered (pH 4.0–4.4) medium, XTT reductase activity was largely dependent onCaFRE10. XTT reductase activity ofC. albicansgrown in medium buffered to pH 6.8 was independent ofCaFRE10but, nonetheless, was upregulated in cells deprived of iron. Reduction of 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT), a membrane-permeable tetrazolium salt, occurred at an intracellular location and was independent ofCaFRE10. However, MTT activity was induced by iron deprivation inC. albicansbut not inS. cerevisiae.C. albicanspossessed multiple iron- and pH-regulated reductase activities capable of reducing tetrazolium salts, but, when grown in unbuffered medium,CaFRE10was required for XTT reductase activity.
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36 articles.
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