Ultrastructural morphometric analysis of thymus epithelial cells two months after pinealectomy

The late effect of surgical ablation of the pineal gland on the morphometric changes of epithelial cells of rat thymus were investigated. The aim of this study was to determine a possible existence of sex related changes in the thymus epithelial cell after pinealectomy and to possibly clarify the correlation between the pineal gland and the thymus. Stereological ultrastructural parameters of the thymus cortical and medullar epithelial cells of male and female rats two months after pinealectomy are reported. A group of animals was submitted to surgery for ablation of pineal gland. The control group (shame-pinealectomized animals) underwent to the same surgical procedure but without removal of pineal gland. Animals were sacrificed 60th days after surgery. Para-sagittal thymus specimens were fixed by immersion in glutaraldehyde and processed for transmission electron microscopy. The volume and surface density (Vv, Sv) of nucleus and cytoplasm of cortical and medullar thymus epithelial cells were calculated using the Weibel's multipurpose test system and multilevel sampling technique on electron micrographs. Volume and surface density of mitochondria (Vvm, Svm), endoplasmic reticulum (Vvr, Svr), vacuole (Vvv) as well as numerical density of mitochondria (Nvm) were evaluated at different magnification levels. Our analysis confirmed a statistically significant increase in Vv of endoplasmic reticulum and vacuoles in both sex of pinealectomized rats. Sv of plasmalema, endoplasmic reticulum and mitochondrial membrane were markedly increased in thymus medullar epithelial cells of pinealectomized rats. Vv of mitochondria was significantly increased in cortical epithelial cells of pinealectomized animals. These results confirm that a correlation between pineal gland and thymus exists. However the present findings seem to support the concept of sex independent inhibitory action of pineal gland on thymus cortical and medullar epithelial cells.