Nitroaryl compounds as potential fluorescent probes for hypoxia. II. Identification and properties of reductive...

Nitroakridin 3582 (NA) and a nitronaphthalimide (DM113), which fluoresce only upon reduction, have been studied by HPLC. V79-379A cells incubated with NA under 20% or 2% O2 and N2 gave increasing amounts of the fluorescent amine with an hypoxic:oxic differential of 160. Measurement of the uptake of NA showed that it was concentrated within the cell by over 1000-fold. Studies in 3 different cell lines of reduction under hypoxia showed a 7-fold range in amine production. DM113 yields more than one fluorescent product, which show different absorption and fluorescence spectra. Chemical reduction of NA or DM113 using a variety of methods gave, depending on conditions, amine and/or (what was presumed to be) hydroxylamine; the latter was non-fluorescent. In vivo, NA is toxic at greater than 0.19 mumol g-1. At this dose much of the drug is found in the liver and kidneys. Plasma levels at 30 minutes are only 2 microM while tumor concentrations are 10 microM compared to 600 microM in the liver. However, the half life is greater than 1 hr and amine was detectable in these tumors.