Polarographic measurement of misonidazole in mouse mammary tumors.

The sensitizing effect of misonidazole, a hypoxic cell radiosensitizer, is presumed to be due to its strong electron affinity. The concentration of misonidazole in mouse mammary tumors was measured polarographically in vivo. When 1 mg of misonidazole per gram body weight was administered intraperitoneally to C3H/He mice, 0.5-0.75 mM of misonidazole was observed in the tumors 25-60 min later. The distribution of misonidazole in the tumors varied, but the mean concentrations were not significantly different except in the necrotic area and the central-superficial region, where the concentration of misonidazole tended to be lower than in the other regions. No differences in the concentration of misonidazole were observed in tumors with diameters ranging from 4 to 11 mm. The polarographic measurement of misonidazole in vivo is technically simple and can be applied to the study of hypoxic cells in tumor tissue.