[Effects of cold exposure on estrous cycle of female C57BL/6 mice].

OBJECTIVE: To study the effects of cold exposure on estrous cycle of female C57BL/6 mice. METHODS: Twelve healthy female C57BL/6 mice were randomly divided into two groups: control group and cold exposure group, 6 in each group. Cold exposure group was exposed to 4℃, 4 h per day, while control group stayed in normal conditions. Vaginal smears were used to observe the estrous cycle. After 2 weeks, blood and uteri were collected from each mouse after anesthetized and weighted. Serum levels of estradiol(E2), follicle-stimulating hormone(FSH), luteinizing hormone(LH), prolactin(Prl) and progesterone(P) were determined by using mouse ELISA kits. The uterus and ovary pathological slices were prepared to observe the structural changes. RESULTS: Compared with the control group, body weight gain showed no significant differences (P＞0.05). The cold group had significant lower coefficients of uterus and the diestrus phase was significantly increased after cold exposure (P＜0.01). Serum level of FSH in cold group was higher and Prl was lower significantly (P＜0.01). Pathological examination of uterus and ovary showed that uterine glands of cold group were expanded and the amount of follicles was decreased significantly. CONCLUSION: Cold exposure might increase mouse estrous cycle and affect their reproductive function.