Rat pineal cell aggregates: Ultrastructural and functional characteristics

Abstract

The aggregates were obtained by constant gyratory shaking of suspension cells freshly isolated from adult rat pineal glands. Their sizes ranged from 60 to 120 μm. Within 4–5 days, the aggregates formed by pinealocytes, astrocytes, and other unidentified cells became organized in a tissue-like configuration. There was no proliferation of the fibroblast cells. Ultrastructural characteristics of the aggregates were revealed by the presence of granular lysosomes, which are typical of pinealocytes, and are actively involved in the secretion. Functional characteristics were studied in static incubation. The aggregates secreted melatonin and other indole amines in culture medium. Basal melatonin release was detected until Day 24 of culture. This secretion was stimulated 230% with Isoproterenol (β-adrenergic agonist), 725% with Epinephrine (α- and β-adrenergic agonists), and 140% with Vasoactive Intestinal Peptide after 5 days in culture, then > 1200% with Forskolin 9 days later (14-day-old aggregates). The results indicate that three-dimensional aggregates obtained from isolated pineal gland cells were the functional multicellular structures with in vivo characteristics.