Ultrastructure of pinealocytes in mice implanted with Colon 38 adenocarcinoma

Relationship between the pineal gland and neoplastic disease has been repeatedly shown in many both experimental and clinical studies. However, morphological studies of the pineal gland in animals with experimentally-induced tumors are rare. Therefore, we decided to investigate the ultrastructure of pinealocytes in mice with implanted Colon 38 adenocarcinoma.

Male adult B6D2F1 mice were used in this study. The animals were divided into two groups. Eight mice were subcutaneously implanted with Colon 38 cell suspension, whereas the other eight intact animals served as controls. Three weeks after tumor implantation four animals from each group were sacrificed by spinal cord dislocation at 12:00 h or 24:00 h. The pineal glands were removed and processed for electron microscopic studies. The cross-sectional areas of the pinealocyte and its nucleus, and relative volume of mitochondria, Golgi apparatus, lysosomes, granular endoplasmic reticulum, and lipid droplets, as well as the number of dense-core vesicles were estimated using a digital analyzer connected on-line to IBM-PC computer. Statistical analysis of the data was performed using Student's t-test and Snedecor F test.

In the pineal glands of the tumor-bearing animals killed during the daytime diminished size of pinealocytes and their nuclei, decreased relative volume of granular endoplasmic reticulum, lysosomes, and lipid droplets as well as decreased number of dense-core vesicles were observed. On the contrary, the relative volumes of mitochondria and Golgi apparatus were increased in these animals. In the tumor-bearing animals killed at night, however, increased cross-sectional areas of pinealocytes, and decreased number of dense-core vesicles were observed.

The results of our study suggest that the presence of the malignant tumor influences the morphology of pineal cells in mice. Considering the fact that different patterns of ultrastructural changes were demonstrated in pinealocytes in different tumor types in various species, it seems that the character of the ultrastructural changes observed in tumor-bearing animals depends on the animal species and tumor type.