Cytochemical analysis of calcium distribution in the superficial pineal gland of the Mongolian gerbil.

The potassium pyroantimonate-osmium method was employed to determine the distribution of cations in the superficial pineal gland of the Mongolian gerbil. The reaction product in the glands was presumed to be calcium following the use of both the chelator EGTA and x-ray microanalysis. A gradient of reaction product was found in the pineal with the highest concentrations occurring in and around the pineal concretions (PC). The periphery of mature PC demonstrated a heavy precipitate as did the surrounding pinealocytes. PC-associated pinealocytes contained reaction product in many organelles, including small vesicles that appeared to be opening in the direction of the concretions. The vacuoles of the pinealocytes contained various concentrations of precipitate. The results obtained in the present investigation have led to a hypothesis on the formation of pineal concretions: a pinealocyte vacuole is formed, calcium is transported to the vacuole, the cation content of the vacuole increases, and the cations precipitate into an immature concretion. Fibrillar material and an amorphous substance located within the pinealocyte vacuole appear to form cation containing vesicles that contribute to the periphery of the developing PC, resulting in the continued growth of the concretion.