Effect Of Acute Heat Stress On Physical Response In Tree Sparrow (Passer Montanus)

Temperature is one of environmental factors that have an important influence not only in energy budget and metabolic thermogenesis,but also in organismal free radicals in birds.Expose to heat stress for a long time can affect bird's normal growth and development.In this study,the effects of heat stress on physiological response in resting metabolic rate,antioxidant enzymes and heat shock proteins 70 in the Eurasian tree sparrows(Passer montanus)were examined,and the antioxidant capacity and adaptive mechanism analyzed.Thirty tree sparrows were captured and then transported to the laboratory and maintained in individual enclosures at 25±1?C on a 12:12h light: dark photoperiod with lights on at 0600.Subjects were kept under these conditions for one week,and then randomly assigned to one of five treatment groups,(1)control(25°C)group,(2)heat stress 2H(42°C,2h)group,(3)heat stress 4H(42?C,4h)group,(4)heat stress 6H(42?C,6h)group,and(5)heat stress 12H(42?C,12h)group,respectively.Birds in the heat stress condition underwent a significant increase in body temperature and water intake compared to control group.Furthermore,and birds exposed to heat stress increased superoxide dismutase catalase and malondialdehyde in serum.Liver is one of the largest and most metabolically active organs in birds,it has stronger antioxidant capacity.However,just 2H group of expose to heat stress significantly decreased the glutathione-SH peroxydase relative to the control and this decrease was not sustained for the remaining 12 H of the experiment.It isnoteworthy that a significant decrease in state-4 respiration and cytochrome c oxidase of exposure to heat stress condition and state-4respiration returned to normal after 12 hours.The express level of heat shock protein 70 mRNA increased in 2 hours and less than the normal level after 12 hours.These results suggest that tree sparrows have a significant response to heat stress in high(42°C)ambient temperature.The stress response of tree sparrows experienced sensitive and resistant stages,and have the abilities to cope with acute heat stress.The Eurasian tree sparrows have well self-regulatory mechanism and adaptive ability to high ambient temperature by adjusting its energy metabolism and antioxidant ability.