Oxidative damage in different tissues of neonatal chicks exposed to low environmental temperature.

Maintenance of body temperature in a cold environment is crucial for survival in homeotherms. However, we have previously reported that on exposure to low environmental temperature, neonatal chicks (Gallus gallus) show hypothermia, decreased behavioral activity, and absence of gene transcript enhancement of putative thermogenic proteins, as well as no change in mitochondrial substrate oxidation enzymes. Various metabolic abnormalities and/or tissue damage may also decline the thermogenic capacity of low-temperature-exposed neonatal chicks. Therefore, to investigate oxidative damage in low-temperature-exposed (20 degrees C for 12 h) neonatal chicks, we studied lipid peroxidation when compared to the control chicks kept at thermoneutral temperature (30 degrees C). Malondialdehyde (MDA), was measured in plasma, brain, heart, liver and skeletal muscle (pectoralis superficialis and gastrocnemius). Weight gain and feed consumption did not change when chicks were exposed to low-temperature as compared to that of control chicks. On low-temperature exposure, body temperature was significantly decreased and plasma non-esterified fatty acid level was 1.3-fold higher than that of control chicks. In low-temperature exposed chicks, brain and heart MDA levels were 2.1- and 1.2-fold higher, respectively, than that of control chicks. This increase in MDA levels was not observed in plasma, liver and muscle of low-temperature-exposed chicks. In conclusion, there is evidence of increased lipid peroxidation in brain and heart of neonatal chicks exposed to low-temperature. We hypothesize that this oxidative damage in brain and heart may contribute to the impaired physiological, behavioral and thermoregulatory responses that potentiate the sensitivity to cold exposure.