Objective: The study was performed to analyze the ultrastructure of ovine pinealocytes during the period of postnatal development.
Material and methods: The pineals of newborn, 10-week and one-year old females of the domestic sheep were prepared for ultrastructural investigations. The point count analysis was used in quantitative studies of the pinealocyte substructures.
Results: The prominent feature of pinealocytes in the newborns was the presence of well developed rough endoplasmic reticulum and numerous polysomes. The pinealocyte cytoplasm contained also smooth endoplasmic reticulum, mitochondria, Golgi apparatus, lysosomes, dense core vesicles, multivesicular bodies and lipid droplets. Pinealocytes of the 10-week and 1-year old sheep were characterized by the occurrence of numerous vesicles and short cisterns of smooth endoplasmic reticulum, abundant microtubules and lipid droplets. Pinealocytes of the adult sheep were distinguished by well developed Golgi apparatus, numerous dense core vesicles and multivesicular bodies. The relative volume of rough endoplasmic reticulum in pinealocytes was significantly higher in the newborn sheep than in two other groups. The relative volume of mitochondria was significantly higher in pinealocytes of the 10-week old sheep than the newborns and one-year old animals. The relative volume of Golgi apparatus was significantly higher in the one-year old animals than in two other groups. No differences concern lysosomes. The relative volume of lipid droplets as well as the numerical density of dense core vesicles and multivesicular bodies increased significantly with age.
Conclusion: The ultrastructure of ovine pinealocytes undergoes the marked changes during postnatal development. The changes concern mainly substructures involved in secretory activity.