Markers of lipid peroxidation and α-tocopherol levels in the blood and neoplastic tissue of dogs with malignant mammary gland tumors.

Abstract

BACKGROUND: Excess reactive oxygen species due to oxidative stress and the ensuing lipid peroxidation are believed to be involved in mammary gland tumor (MGT) pathogenesis. OBJECTIVE: The purpose of this study was to evaluate the extent of lipid peroxidation as evidenced by thiobarbituric acid-reactive substances (TBARS) formation, and the concentration of α-tocopherol as an inhibitor of lipid peroxidation, in blood and neoplastic tissue of dogs with malignant MGT. The correlation between inflammatory cell infiltration score and TBARS or α-tocopherol in MGT was also evaluated. METHODS: Sixteen intact female dogs with malignant MGT and 12 clinically healthy and age/weight-matched controls were included in the study. In all dogs, serum TBARS, α-tocopherol, total cholesterol, and triglycerides were measured. Tissue TBARS and α-tocopherol levels were determined in 1 cm(3) sized tissue samples collected from MGT and adjacent, ipsilateral, normal mammary gland tissue from the 16 affected dogs. The degree of inflammatory cell tumor infiltration was evaluated histologically. RESULTS: There were no statistically significant differences in serum levels of TBARS, α-tocopherol, total cholesterol, and triglycerides between dogs with and without malignant MGT. TBARS were significantly higher, whereas α-tocopherol was lower in neoplastic tissue when compared with normal mammary gland tissue. There was no correlation between TBARS or α-tocopherol concentration and the inflammatory cell infiltration score in neoplastic tissue. CONCLUSION: The increased level of TBARS suggests oxidative stress induction in canine malignant MGT. The origin of this phenomenon is not clear, as a potential oxidative burst could not be attributed to inflammatory cells infiltrating the tumors.