Oxidative stress in cancer-bearing dogs assessed by measuring serum malondialdehyde

BACKGROUND Oxidative stress, an excess of reactive oxygen species (ROS), causes lipid peroxidation resulting in cell and tissue damages. It may be associated with the development and progression of cancers in dogs. Malondialdehyde (MDA), the end product of lipid peroxidation, is commonly used as a marker of oxidative stress. The objective of this study was to assess oxidative stress in cancer-bearing dogs by measuring serum MDA levels. All client-owned dogs underwent physical examination at the Veterinary Teaching Hospital, Faculty of Veterinary Medicine, Khon Kaen University to determine the health status with the owner's consent. Blood samples of cancer-bearing dogs (N = 80) and clinically normal dogs (N = 101) were obtained and subjected for determination of MDA levels. In addition, complete blood count, creatinine, and alanine aminotransferase were measured. RESULTS Serum MDA was significantly higher in cancer-bearing dogs than in clinically normal dogs (mean ± SD, 4.68 ± 1.32 μmol/L vs 2.95 ± 0.61 μmol/L, respectively; p < 0.001). Packed cell volume (mean ± SD, 36.18 ± 7.65% vs 44.84 ± 5.54%), hemoglobin (mean ± SD, 11.93 ± 2.88 g% vs 15.17 ± 2.00 g%) and red blood cells (median (IQA), 6.05 (2.15) vs 8.09 (1.34)) were all significantly lower in cancer-bearing dogs than in clinically normal dogs. However, the reverse was true for white blood cells (median (IQA), 18.20 (11.95) vs 14.90 (5.10)). Neither creatinine nor alanine aminotransferase levels were significantly different between groups. CONCLUSIONS This study supports the conclusion that oxidative stress is associated with many types of cancers in dogs, as serum MDA levels were significantly higher in cancer-bearing dogs compared to clinically normal dogs.