Effects of Blue Light on Puberty and Ovary in Female Rats.

PURPOSE: This study was planned to examine the effect of blue light exposure and exposure time on puberty.

METHODS: Eighteen 21-day-old female Sprague Dawley rats were divided into three groups consisting of six rats in each group: Control Group (CG), Blue Light-6 hours (BL-6), and Blue Light-12 hours (BL-12). CG rats were maintained with 12/12-hour light-dark cycles. The rats of BL-6 and BL-12 were exposed to blue light(450-470nm/irradiance level 0.03uW/cm2) for 6 hours and 12 hours, respectively. Rats were exposed to blue light until the first signs of puberty. Serum FSH, LH, Estradiol, testosterone, DHEA-S, leptin, and melatonin were studied by the ELISA method. Ovaries and uterus were dissected for histomorphological examination.

RESULTS: The medians of the pubertal entry days of the CG, BL-6, and BL-12 were 38th ,32th , and 30th days, respectively (p:0.001). The FSH, testosterone, DHEA-S, and leptin concentrations of all groups were similar. However, LH and estradiol concentrations of BL-6 were higher compared to CG. There was a negative correlation between blue light exposure, exposure time, and melatonin concentrations (r=-0.537, p=0.048). Ovarian tissue was compatible with the pubertal period in all groups. As the blue light exposure time increased, capillary dilatation and edema in the ovarian tissue increased. Prolonged exposure caused polycystic ovary-like (PCO) morphological changes and apoptosis in granulosa cells. Our study is the first to show the effects of blue light exposure on puberty.

CONCLUSION: Our study showed that exposure to blue light and the duration of exposure lead to early puberty in female rats. As the duration of blue light exposure increased, PCO-like, inflammation, and apoptosis were detected in the ovaries.