Effects of continuous light exposure on testicular structure and function of the African giant rat (Cricetomys gambianus)

Abstract

The aim of this investigation was to study the effects of continuous lighting exposure on the testes of the African giant rats (AGR). Samples of testes from twelve (12) healthy AGR were investigated under two groups. The rats were divided into two groups of 6 rats each as follows: Group I - Control rats (12 h light/12 h darkness); Group II - Rats exposed to continuous light (24 h). The indices of the testes were length, width, and weight of the organ, estimation of serum levels of testosterone, luteinizing hormones, follicle stimulating hormone (FSH) by radioimmunoassay (RIA) technique and histological studies of the testes. The mean body weight of the rats exposed to continuous light was 1.086 ± 0.034 kg which was reduced by 3.9 % from the control (1.131 ± 0.02 kg). The mean weight of the testes in rats, exposed to continuous light was 4.549 ± 0.30 g, which was significantly reduced by 17.8 %, when compared to the control (5.534 ± 0.16 g). The mean length and width of testes of rats exposed to continuous lighting was 0.294 ± 0.71 cm and 0.143 ± 0.48 cm, respectively. The mean serum level of testosterone in control rats was 1.225 ± 0.08 miu/ml and that in rats exposed to lighting, 0.275 ± 0.10 miu/ml. This result showed that the serum level of testosterone in male rats exposed to continuous lighting was reduced by 77.6 % from 1.225 ± 0.08 miu/ml in the control rats to 0.275 ± 0.10 miu/ml. Histological observations showed that the testes of rats exposed to light displayed elongated to round seminiferous tubules each with wide lumen lined by low germinal epithelium, and had wide interstitial spaces. Disruption of spermatogenesis and vacuolization of epithelial cells were evident. This study has shown that exposure of AGR for four (4) weeks of continuous lighting will result in disruption of spermatogenesis and decreased testosterone serum level.

Keywords: Light; Testes; African giant rat