RESUMO
This study aimed to investigate by using electron microscope and immunohistochemistry, effects of short duration of light exposure on the Leydig cells of rat's testis. It tries to relate between seasonally changed environmental light factor and an important part of male reproductive system. Sixteen adult male albino rats were divided according to light exposure into control group [six rats] exposed to light: dark 12:12 h and group II [ten rats] exposed to light: dark 8:16h, daily for eight weeks. Light was provided by 20 watt fluorescent bulb. Testes Specimens were prepared for electron microscope and paraffin sections were stained for Fas and VEGF immunohistochemistry. Optical density of VEGF immunoreaction in Leydig cells was assessed morphometrically. In group II, the ultrastructural findings showed less mitochondria, smooth endoplasmic cisternae and secretary vesicles. Cytoplasmic vacuoles and irregularity of cell membrane of some Leydig cells were detected. Irregular nuclear membrane and condensation of nuclear chromatin were seen. Immunoreactivity for Fas was positive in some Leydig cells of group II. VEGF immunoreaction was decreased in many Leydig cells and this was proved by a significant decrease in mean optical density of VEGF immunoreaction. Short photoperiod exposure [which reflects short days of the year] may result in hypofunction of the Leydig cells in rat's testis with possible consequent decreased testosterone secretion and reproductive regression. So, seasonal fluctuations in Leydig cells morphology and function may serve to synchronize reproduction with favorable environmental conditions