Modification of superoxide dismutase in rat mammary carcinoma

In female Sprague Dawley rats, the tissue protein is homogeneously distributed and significantly increased in 7,12-dimethylbenz[a]anthracene-initiated mammary carcinoma. At the centre and margin of the carcinoma, the concentration of superoxide dismutase is 54 +/- 10 and 117 +/- 38 microgram/g, respectively, while in the tumour as a whole it is 104 +/- 32 microgram/g. The latter value is not significantly different from 113 +/- 35 microgram/g, the enzyme concentration in mammary tissue from lactating rats. Exposure of the tumour-bearing rats to hyperoxia does not increase the tumour protein but raises the enzyme concentration at the centre and margin of the carcinoma to 162 +/- 73 and 286 +/- 103 microgram/g, respectively.