The Effects of Estrogen and Antiestrogens on Light-Induced Retinal Damage in Rat
The effect of an overdose of estrogen (polyestradiolphosphate, 0.5 and 2.0 mg/kg) as well as two antiestrogens tamoxifen and toremifen (5 and 25 mg/kg) on the outer nuclear layer (ONL) of the retina were investigated both with rhythmic illumination (12 h/12 h, 300–550 lux) and with continuous illumination (1800–2000 lux) in mature female Sprague-Dawley rats. The daily dosing periods were 1–12 days and 26–28 days. With rhythmic illumination, the ONL remained normal with all treatments for the 28 days. Under continuous illumination, the light induced an expected decrease of the cell layers of the ONL in the control group. When estrogen (2.0 mg/kg) was administered, the cell layers of the ONL decreased significantly within 12 days (p < 0.001). With antiestrogens tamoxifen and toremifen the cell layers of the ONL were significantly decreased with the higher dose used (25 mg/kg) within 12 days (p < 0.05). In conclusion, estrogen alone did not damage the photoreceptors of the retina. Its damaging effect appeared only together with continuous illumination. The treatment of rats with antiestrogens could not prevent or delay the damaging effect of the continuous illumination to the ONL of rat retina.