Effects of cold stress on nitric oxide in duodenum of chicks.

Animals may suffer from a variety of environmental stressors every day, among which is cold stress, which commonly exists in cold regions. The aim of this study was to investigate changes in antioxidative function and inducible nitric oxide synthase-nitric oxide (iNOS-NO) system activity in the duodenum of chicks as a reaction to cold stress. A total of 84 male chicks (15 d old) were randomly allocated to 12 groups (7 chickens/group). There were 1 control group and 5 treatment groups for acute cold stress and 3 control groups and 3 treatment groups for chronic cold stress. Antioxidative function was examined by superoxide dismutase (SOD), and oxidative damage was examined by malondialdehyde (MDA) detection. The iNOS-NO system activity was identified by NO content and NOS activity assay, and the transcription of iNOS mRNA was tested by fluorescence quantitative PCR. The results showed that under acute cold stress MDA level increased, the activity of NO in the duodenum fluctuated, and the activity of SOD and iNOS in the duodenum first increased and then decreased, whereas the expression of iNOS mRNA decreased. Under chronic cold stress the activity of SOD, NO, and NOS first decreased and then increased, whereas the MDA level and the expression of iNOS mRNA increased. The results indicated that both acute and chronic cold stress could cause duodenum oxidative stress and change in iNOS, which was related to the intestinal damage process.