Trans10, cis12-conjugated linoleic acid exhibits a stronger antioxidant capacity than cis9, trans11-conjugated linoleic acid in primary cultures of laying hen hepatocytes.

The objective of this study consisting of 2 trials was to investigate the antioxidant role of conjugated linoleic acid (CLA) isomers (c9, t11-CLA and t10, c12-CLA) and the underlying mechanism by which they act in modulating redox status in a primary laying hen hepatocyte culture. In trial 1, the cytotoxicity of CLA isomers or linoleic acid (LA) (0, 25, 50, 100, 200, 400, 800 µmol/L) was evaluated by 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay. The concentration of CLA isomers or LA (25, 50, 100 µmol/L) for proper antioxidant activity was evaluated by measuring the antioxidant enzyme activity. In trial 2, there were 5 groups: control group, cells were untreated; H2O2 group, cells were exposed to 4 mmol/L H2O2 for 2 h; c9, t11 or t10, c12 or LA group, cells were treated with c9, t11-CLA or t10, c12-CLA or LA for 24 h and then exposed to 4 mmol/L H2O2 for 2 h. Trial 1 showed that the non-toxic dose range for CLA isomers was 0 to 200 µmol/L. The optimum concentration of c9, t11-CLA and t10, c12-CLA for trial 2 was 100 µmol/L. In trial 2, pretreatment with t10, c12-CLA but not c9, t11-CLA attenuated the increase in reactive oxygen species (ROS) compared to hydrogen peroxide (H2O2) group (P < 0.05). t10, c12-CLA elevated the superoxide dismutase (SOD) and catalase (CAT) activities compared with the H2O2 group (P < 0.05). In addition, t10, c12-CLA up-regulated the mRNA expression of nuclear factor E2-related factor-2 (Nrf2) as well as its target genes, Cu-Zn superoxide dismutase (SOD1) and CAT (P < 0.05). Pretreatment with t10, c12-CLA but not c9, t11-CLA decreased Nrf2 protein expression in the cytoplasm and increased Nrf2 protein expression in the nucleus compared with the H2O2 group (P < 0.05). The results indicate that t10, c12-CLA exhibits a stronger antioxidant capacity than c9, t11-CLA in primary cultured laying hen hepatocytes. t10, c12-CLA increases the activity and mRNA expression of antioxidant enzymes via facilitating nuclear translocation of Nrf2.

Low-current & high-frequency electrical stunning increased oxidative stress, lipid peroxidation, and gene transcription of the mitogen-activated protein kinase/nuclear factor-erythroid 2-related factor 2/antioxidant responsive element (MAPK/Nrf2/ARE) signaling pathway in breast muscle of broilers.

Mechanism of electrical stunning (ES) methods on lipid peroxidation and antioxidant protection were studied by determining meat color, serum variables, antioxidant-related enzyme activities, gene expressions of mitogen-activated protein kinases (MAPKs), nuclear factor-erythroid 2-related factor 2 (Nrf2), glutathione S-transferases (GSTs), and superoxide dismutases (SODs). Broilers were sacrificed without stunning, or after ES with 65V, 86mA, 1000Hz (E65V) or 150V, 130mA, 60Hz (E150V). Serum cortisol and uric acid, muscular malondialdehyde and mRNA levels of MAPKs, Nrf2, GSTA3, GSTT1 and SOD2 were increased, whereas, serum free triiodothyronine, free thyroxine, muscular GST1d activity were decreased in E65V compared with E150V. Overall, the serum uric acid and transcription of the MAPK/Nrf2/ARE (antioxidant responsive element) signaling pathway were elevated, but didn't overcome the oxidative stress stimulated by low-current & high-frequency ES, leading to aggravated lipid peroxidation at 1d and 9d postmortem in breast muscle compared with high-current & low-frequency ES.

Toxicity of dietary melamine to laying ducks: biochemical and histopathological changes and residue in eggs.

Jinding laying ducks (n = 648) were subjected to one of six dietary treatments (0, 1, 5, 25, 50, or 100 mg of melamine/kg of diet) to investigate the toxicity of melamine and determine the melamine residue in eggs. Ducks were fed melamine-supplemented diets for 21 days followed by a 21 day withdrawal period. Dietary melamine had no adverse effects on laying performance. Renal lesions were correlated with increasing levels of dietary melamine. Melamine residue in eggs increased with dietary melamine during the first 21 days and reached the maximum content (1.35 mg/kg) in the 100 mg of melamine/kg of diet group. Melamine residue in eggs decreased rapidly during the withdrawal period. The depletion time for egg melamine residue increased with dietary melamine level. These results indicated that a dietary level of > or = 50 mg of melamine/kg of feed induces obvious renal injury. The residue level and withdrawal time for melamine clearance in eggs correlated with the dietary melamine level.