ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of acute heat stress on the day-night circadian gene Per2 mRNA expression in the liver of rats.</p><p><b>METHODS</b>Male Wistar rats were randomly divided into two groups and exposed to heat at 32 degrees celsius; or to a room temperature at 24 degrees celsius; (control). After 7 days of heat exposure, the body temperature was measured by telemetry. The relative weight of the pituitary and adrenal glands was determined after the exposure, and liver Per2 mRNA expression level was detected using RT-PCR.</p><p><b>RESULTS</b>Acute heat stress did not obviously affect body temperature or body weight of the rats. Seven days of heat exposure increased the relative weight of the pituitary and adrenal glands and significantly lowered Per2 mRNA expression level at night.</p><p><b>CONCLUSION</b>Acute heat stress can interfere with the day-night circadian gene Per2 mRNA expression in rats.</p>