The aim of this study was to determine whether photoperiodism has any impact on the effects that three-month long exposure to extremely low frequency electromagnetic field has on morphological characteristics of rat's pineal gland.
The exposure was carried out on 24 male rats starting 24 hours upon birth until their sexual maturity. The control group consisted of 24 male rats as well. The study was performed both during summer and winter, following the identical protocol. Six animals each per exposure group and control group were investigated first in each season (summer/winter) directly after exposure (group I) and second after three weeks of exposure (group II).
Concerning wintertime, the most significant morphological changes in pineal gland in group I of exposed rats were: hyperemia, reduced pinealocytes with pale pink, poor cytoplasm and irregular, stick-form nuclei. In group II pinealocytes were enlarged, with vacuolated cytoplasm and hyper chromatic, enlarged nucleus. Morphological changes of the pineal gland in the summer were not as intense as in the winter and finding in the group II was comparable with those from the control group.
Stereological investigations revealed a decrease of volume density of pinealocytes, their cytoplasm and nuclei in group I both in winter and summer. In group II in winter, a volume density increase of pinealocytes, cytoplasm and nuclei was found.
These results indicate that photoperiodism is a modifier of the effect of extremely low frequency electromagnetic field on morphological structure of pineal gland, as the gland recovery was incomplete in winter and reversible in summer.