RESUMEN
Exposure of living organisms to a constant generation of reactive oxygen species (ROS) resulted in the development of antioxidative defence systems which protect cells and tissues against their harmful effects. The retention of fetal membranes (RFM) in cows is hypothesized to be connected with the imbalance between production and neutralization of ROS. The efficiency of enzymatic and non-enzymatic antioxidative systems can be detected by the determination of single components of this system or by so-called total antioxidant capacity (TAC). In the present study, total antioxidant capacity was compared with previously measured parameters of antioxidative defence mechanisms in placental tissues of cows with respect to time of fetal membranes expulsion and mode of delivery. Placental samples were divided into: (A) caesarian section before term (272-277 days of pregnancy) without RFM (n=9), (B) caesarian section before term with RFM (n=14), (C) caesarian section at term (282-288 days of pregnancy) without RFM (n=12), (D) caesarian section at term with RFM (n=16), (E) spontaneous delivery at term without RFM (n=8), (F) spontaneous delivery at term with RFM (n=8). TAC was measured spectrophotometrically at 593nm by use of 2,4,6-tri-pyridyl-s-triazine in homogenates of maternal and fetal part of placenta and expressed as mumol/g protein (mean+/-S.E.M.). The values of TAC were significantly higher (P
RESUMEN
The aim of the present study was to describe some of the oxidative stress parameters in bitches suffering from spontaneously occurring mammary gland tumours. The experiment involved 28 bitches which had mammary gland tumours removed surgically (15 bitches with malignant tumour and 13 with benign tumour) as well as 10 clinically healthy bitches. The activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) were determined in haemolysates of erythrocytes derived from the animals. The concentrations of thiobarbituric acid reactive substances (TBARS), as well as -SH groups, were determined in blood plasma. GSH-Px activity was significantly higher in the malignant tumour group than in healthy animals. SOD activity was significantly higher in animals with tumours compared with the control group. Activities of both enzymes were higher in animals with malignant tumours than in benign groups, but the differences were not statistically significant. The concentrations of TBARS and -SH groups were similar in all examined groups. The increase of antioxidative enzyme activities in these animals may suggest the activation of antioxidative defence mechanisms in mammary gland carcinogenesis. Moreover, it might indicate the participation of oxidative stress in malignancies. Further experiments involving more animals, with more frequent sample collection and the use of other oxidative stress markers are necessary.
