The aim of this study was to reveal whether there is a difference between expression of the liver Heat Shock Protein 70 (HSP 70) and gender in rats exposed to cold stress by using histopathological and immunohistochemical techniques. The study was performed on totally 40 Sprague-Dawley rats [24-week old male (n=20) and female (n=20) rats weighing ~200 and ~220 g, respectively]. The rats were divided into four groups randomly; each group consisted of ten rats (n=10). The first (female) and second (male) groups were accepted as control groups and the third (female) and fourth (male) groups were considered as stress groups. The rats in the third (stress female) and fourth (stress male) groups were exposed to cold (4ºC) 2h/day for 10 days. Then, all of the groups were sacrificed and the livers were collected for histopathological and immunohistochemical evaluations. Histopathological examination of the control group animals showed normal hepatic tissue histology. By contrast, histopathological examination of the stress group animals demonstrated prominent degenerative changes. There were no statistically significant differences in livers of the male and the female stress groups in terms of histopathological changes. The expression of HSP 70 in varying degrees was determined in the liver of both control and stress groups. As severity of lesion increased, the expression of HSP 70 decreased at the same rate. The expression of HSP 70 in livers of the female rats was higher than that of the male rats (P<0.05).

Key words: Cold stress, Gender, HSP 70, Liver, Rat