A suspension culture of pinealocytes: regulation of N-acetyltransferase activity.

A method to prepare suspension cultures of highly viable pinealocytes is described. Pineal glands of neonatal or adult rats can be used; the best yield is obtained from neonatal glands. Morphological examination of the cells indicates that they have a normal, healthy appearance and retain some structures typical of neonatal pinealocytes. During the first 24 h of culture, the cells aggregate into small clusters; after several days, larger aggregates can be seen. Biochemical studies indicate that adrenergic stimulation of these cells causes a 30- to 100-fold increase in serotonin N-acetyltransferase activity, a response which is unique to the pineal gland. The relative order of potency of several adrenergic agonists is l-isoproterenol greater than l-norepinephrine greater than or equal to l-epinephrine greater than phenylephrine. Serotonin, tyramine, histamine, carbachol, gamma-aminobutyric acid, cocaine, and desmethylimipramine are inactive. Studies using adrenergic and metabolic inhibitors indicate that the regulation of N-acetyltransferase in these cells has the same characteristics of that seen in adult tissue. In addition, these cells synthesize protein and RNA from radioactive precursors, convert tryptophan to serotonin, and N-acetylate endogenous serotonin.