β‐Adrenergic stimulation increases cAMP and melatonin production in ovine pinealocyte cultures

An ovine pinealocyte suspension culture method, using glands from young sheep as a source of cells, has been developed to study mechanisms of pineal regulation in this species. Cell suspensions are obtained by enzymatic digestion (preliminary trypsinization followed by collagenase/pronase treatment) of pineal glands and these cells may be usefully retained in culture for up to 48 hr. Initial characterization of cyclic adenosine monophosphate and melatonin production responses to adrenergic stimuli (norepinephrine, phenylephrine, isoproterenol) in the absence and presence of antagonists (propranolol, prazosin) by pinealocytes in suspension culture indicate that a beta-adrenergic receptor-mediated mechanism is primarily involved in transduction of the adrenergic signal to melatonin synthesis. This is in agreement with data from earlier work on the sheep using short-term tissue incubations but contrasts with in vivo evidence suggesting a predominant alpha 1-adrenergic receptor-mediated mechanism.