人工光照对青春期前雌性大鼠生殖系统发育的影响

Effects of artificial lighting on the development of reproductive system in preadolescent female rats

目的研究人工光照时长对青春期前雌性大鼠生殖系统发育的影响。方法选取40只离乳后(日龄为21天)的SPF级雌性大鼠,随机分成对照组、16h光照组、20h光照组、24h持续光照组,每组10只。各组均正常饮食,持续28天。阴道涂片法检测动情周期,计算卵巢和子宫脏器系数,酶联免疫吸附法(ELISA)检测血清中褪黑素(MT)、卵泡刺激素(FSH)雌二醇(E2)水平,HE染色显微镜下观察卵巢和子宫组织形态学的改变。结果与对照组相比,24h持续光照组动情期延长,卵巢和子宫脏器系数升高,MT下降,E2水平增高,可见成熟卵泡和排卵后黄体;除20h光照组偶见少量成熟卵泡外,16h光照组和20h光照组卵巢和子宫脏器系数和血清激素水平未见明显改变。结论一定范围内延长光照对雌性大鼠生殖系统发育无显著影响,但24h持续人工光照可以导致青春期前雌性大鼠性发育提前,这可能与体内MT水平抑制有关。

Objective To investigate the effects of artificial lighting on the development of reproductive system in preadolescent female rats. Methods Forty healthy 21-day-old female rats in SPF grade were randomly divided into 4 groups （10 rats each）： control group and groups that were continuously exposed to light for 16, 20 or 24 hours on a daily basis. All rats were given normal diet. After 28 days, the pattern of vaginal cell exfoliation during the estrous cycle period was studied, and the organ indexes of ovary and uterus were calculated. The serum concentrations of melatonin （MT）, estradiol （E2）, follicle-stimulating hormone （FSH） were quantified by ELISA, and the histopathological lesion of uterus and ovary were observed with HE staining. Results Compared to control, rats in 24-hour light exposure group had a prolonged estrous cycle and increased organ indexes of ovary and uterus. Their serum concentrations of MT decreased while E2 increased. Mature follicles and corpus luteum after ovulation were visible. In contrast, 16-hour and 20-hour light exposure groups had no obvious changes on their reproductive activities. Conclusion The moderately increased exposure to artificial lighting had no obvious effect on the development of reproductive system in preadolescent female rats, but 24 hour continuous exposure induced a premature development, which may be associated with the reduction of melatonin level.